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 wereprepared for the densification of the yeast solution. By non-solvent phase inversion method (NIPS), the PLACS microfiltrationmembranes were prepared by using chitosan (CS) acetic acid solution as the coagulation bath and glutaraldehydeas the crosslinking agent. PLACS membranes were characterized by water contact angle, porosity, pore sizedistribution, mechanical properties, ATR-FTIR, SEM, TGA and the ultrafiltration experiment. The viscosity of coagulationbath solution can severely influence the exchange rate of the solvent and the non-solvent as well during phaseinversion; 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) contentincreased, gel rate became smaller and membrane forming process was prolonged; the porosity and pore size of thePLACS were increased compared to the polylactic acid (PLA) membrane, pure water flux increased from 90.31 L·m2·h1to 120.14 L·m2·h1, and yeast rejection rate increased from 75% to more than 90%.