Poly(ether sulfone) (PES) ultrafiltration membranes are fabricated via nonsolvent-induced phase separation by blending with hydrophilic homopolymer additive poly(ethylene glycol) (PEG) or amphiphilic block copolymer Pluronic F127. The effects of coagulation bath temperature (CBT) on membrane structure, separation performance, and antifouling property are investigated in detail. All the membranes display an asymmetric morphology. PES/PEG membranes possess only fingerlike pores of support layer, while there is a spongelike sublayer between skin layer and the fingerlike pores for PES/Pluronic F127 membranes. The thickness of the spongelike sublayer for PES/Pluronic F127 membranes is remarkablely decreased with the increase of CBT. For all the membranes, pure water flux increases substantially with the increase of CBT. The rejection of PES/PEG membrane for bovine serum albumin (BSA) is above 95%. However, the rejection of PES/Pluronic F127 membrane for BSA molecules is decreased sharply form 95.3% to 10.2% with the increase of CBT from 20 to 60 degrees C. At higher CBT, the antifouling capabilities of PES/Pluronic F127 membranes are slightly weakened mainly because of the lower surface coverage of amphiphilic copolymer.