Polyethersulfone hollow fiber membranes were prepared from polyethersulfone/N, N-Dimethylacctamide/poly (N-vinyl-2-pyrrolidinone) systems by dry/wet phase inversion process using water as coagulation bath. The effects of coagulation bath temperature and air gap distance on the surface structure, cross section structure and water flux of membranes were discussed. As increasing the temperature of coagulation bath and the air gap distance, the size of the pores at the surface effectively increased, while the finger-like structure under the outer surface changed to a sponge-like structure.