Forewarned is forearmed: It looks like you're using at least one mod, since turn order isn't normally displayed. I play the game as-is, so if the mod makes any changes in the areas I touch on, my answers will be wrong for you.
ngoncom: - Case 1, I attack first: Force Field seem protect Zealot and Archangels very ok. But when turn 2 start, Force Field disappear and I want to cast it again, I can't do that because enemy's Gold Dragon attack first. So I am wonder how to prevent Force Field as long enough to my turn, so I can cast it again.
Force Field always fades after two turns, where the counting starts on the turn it is cast. This is a limitation of the spell which is pretty much necessary to keep a hero with high spell power and high knowledge from effectively permanently blocking off portions of the battle field.
Unit action order requires something of a lengthy explanation because it involves a number of variables. If his Gold Dragons get their action in a round before your Arch Angels have an action, then either your AA have been slowed (which will be obvious if it happens) or the enemy has one or two artifacts that give his units a total of +2 speed.
I'm assuming the AA have not been slowed. If they have, then any of several spells will fix that (examples include haste, cure, and dispel), and you need to cast one of them after the slow and before the third round when you want to cast another force field.
Therefore, there are three ways to get the AA to act before the GD while both units have the same speed.
1) Kill all the GD's. Obviously they can't act if they are all dead. Since your screenshot shows 221 of them, this doesn't seem feasible.
2) Cast Haste or Prayer on your AA, increasing their speed. Wait until he has cast his spell in the second round, and he won't be able to cast anything to counter your spell.
3) Make sure that the last unit to act in Round 2 is one of his units. This includes war machines (your First Aid Tent)! When two units on opposite sides of a battle have equal speed, the tie is decided in favor of the side that did NOT act previously. If the AA and GD are acting on the same initiative count, then the one that acts first is whichever one did not have an ally creature act last in the previous round. For example, if your dendroids took the very last action (whatever it may be) at the end of Round 2, then the GD's act first in Round 3 since priority in ties would go to their side. If their dendroids acted last at the end of Round 2, then your team would have priority in breaking the tie.
Looking at the unit counts, you probably already know most of this next bit, but I'll cover it all for completeness sake. There are three turn order phases each round.
A) Normal turn order.
B) Good Morale-Waited turn order.
C) Waited turn order.
In the Normal turn order, every unit acts on its initiative count, with the game starting at the highest initiative and counting down. If two or more creatures on the same side have the same initiative, then the tie breaker is their vertical starting position in the battle, where the units nearer the top of the battle map go first. If units on opposing sides of the battle have the same initiative, then (as above) the tie breaker is lost by whichever side had a unit act most recently; if no units have acted in the battle yet, then the attacker gets priority.
If a unit waits during the normal turn order, then they are placed in the Waited turn order queue. If the unit acted, got Good Morale to act again, and chose to wait during their morale action, then they are placed in the Good Morale Wait turn order.
Only units that got Good Morale and then Waited during the normal turn order will act during the Good Morale-Wait queue. Beyond that, I'm not sure whether it works like the normal turn order (higher initiative goes first) or the Wait turn order (lower initiative goes first). Since most units that get Good Morale want to repeat their previous action (like repeating an attack on a target they just attacked), this queue is usually empty.
The Wait turn order works the same as the Normal turn order, with two exceptions. 1) Only units that haven't acted yet will get an action, and 2) the game starts with the lowest initiative count and counts up, so slower units act before faster units.
ngoncom: - Case 1, I attack later (defense hero): this case Force Field seem not worth anymore, see this image:
https://imgur.com/a/CUVuAw4. Force Field reverse, so there are many space for enemy's creatures can attack my Archangels.
Force Fields always take the same shape, regardless of whether the caster is the the Attacker or Defender. Its shape only depends on the caster's skill in Earth Magic, which determines whether it occupies one hex or two hexes.
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Honestly, looking just at the Attack and Defense of each hero and the creature numbers I can see, this doesn't look like a fight you can win in straight combat. It will come down to which spells each of you have. Skip Force Field for now; it has some amazing utility in certain circumstances, but what you need right now are spells that have a much more overwhelming effect on the numbers of creatures doing battle. Blind, Forgetfulness, and especially Expert Berserk would work wonders on making his Grand Elves less of a problem; they'll easily go right through a force field to hit targets of opportunity. Expert Resurrection would go a huge way toward mitigating your losses, while an elemental summon spell would give you a stack to soak up their retaliations before the rest of your units pile on the victim. Clone could also soak retaliations, but it isn't as efficient about it as a strong elemental summon.
The magic resistance of the Battle Dwarves and War Unicorns is going to be a big problem, giving them a chance at shrugging off your spells as critical times. Some buff spells like Expert Bless would be a great help to your units.
