Is this good build for Nasus?

eh...I mean in the greater scheme of things

no

but in a extremely situational scheme of things, maybe

if you are going tank susan (which i'm assuming due to the loadout)

a more opportune and useful rounded build would be

you basically just want to be a giant shield for your team, taking as much damage as possible and the only damage you need is from your Q stacks

If it works for you keep doing it if not switch trinity out for switch steraks out for another MR/Amor item.

i would like thornmail too but i'm aiming for max cdr so i dunno

Physical damage is far more threatening to Nasus than magic damage, so you're going to want more armor than what that build will give. Randuin's is a must build against most teams. Frozen Fist is better than Trinity Force.