In order to slow down the mass exchange between solvent and non-solvent during nonsolvent induced phase separation and delay the phase transition process, evaporation-induced phase separation was introduced before the casting solution was immersed in the coagulation bath. The internal structure and properties of polysulfone membranes were changed by adjusting the evaporation induction time, ambient temperature and humidity. The results show that the mass of the casting solution increases approximately linearly with the increase of pre-evaporation time, and the rate of water vapor immersion into the casting solution is higher than that of solvent evaporation in the casting solution. Meanwhile, the cross-sectional morphology shows that the shape of membrane pores gradually changes from typical finger-like pores to cellular round pores of uniform size, and the thickness of cellular round pores in the epidermal layer also increases throughout the membrane cross-section until the finger-like pores in the membrane cross-section gradually disappear at 25 min. The increase in ambient temperature (decrease in humidity) accelerates the mass exchange between NMP and water vapor leading to the appearance of finger pore structures. The porosity is decreased from 78.39% to 61.12% at the same evaporation temperature, the average through-pore size is decreased from 0.0616 μm to 0.0219 μm, and the water flux decreased from 948.85 L/(m2·h) to 4.533 L/(m2·h). However, the mechanical properties of the membranes are all improved after the pre-evaporation process.