energy shield mod does not work

My helmet has 74% energy shield increase mod, but
with / without the helmet, my energy shield is the same.

Increased ES mods on gear are local modifiers, means they only affect the base defence stat of the gear piece. If you have a pure armor helmet and craft 74% increased ES mod on it then that will have no effect because the helm has no base energyshield and 0 increased by 74% is still zero.

wow, thanks!
I added this mod at crafting bench, and did not know it worked only with local. Is there any global way to increase ES?

Amulets can have increased ES as a global mod if i am not mistaken. Maybe belts/rings can also have an increased ES mod, you can check that kind of stuff on craftofexile.com.
Generally, any gear piece that has the corresponding def stat will only get increases to it as local mods so body armor/helm/gloves/boots won't work outside of special cases like the 50% inceased global defense mod on breach body armors.

the mod 'increased *maximum* energy shield' on this type of belt, applies to your total ES, not locally.