Membrane hydrophilicity is a crucial factor in evaluating ultrafiltration processes. In this paper, chitosan (CS) was selected for the hydrophilic modification of the polylactic acid (PLA) membrane, and PLACS membranes were prepared for the densification of the yeast solution. By non-solvent phase inversion method (NIPS), the PLACS microfiltration membranes were prepared by using chitosan (CS) acetic acid solution as the coagulation bath and glutaraldehyde as the crosslinking agent. PLACS membranes were characterized by water contact angle, porosity, pore size distribution, mechanical properties, ATR-FTIR, SEM, TGA and the ultrafiltration experiment. The viscosity of coagulation bath solution can severely influence the exchange rate of the solvent and the non-solvent as well during phase inversion; therefore, it can regulate the precipitation kinetics and membrane morphology. The results showed that chitosan (CS) was presented as granular on the pore surfaces of the PLACS membranes. When chitosan (CS) content increased, gel rate became smaller and membrane forming process was prolonged; the porosity and pore size of the PLACS were increased compared to the polylactic acid (PLA) membrane, pure water flux increased from 90.31 L· m-2· h-1 to 120.14 L· m-2· -1, and yeast rejection rate increased from 75% to more than 90%.