A novel pressure control method (constant-flow pump) was introduced to conventional membrane emulsification, for precisely controlling the transmembrane pressure of the dispersed phase, named novel membrane emulsification. Poly(lactic-co-glycolic acid) (PLGA) microspheres was prepared by oil-in-water emulsion method respectively, based on conventional membrane emulsification and novel membrane emulsification. Compared with conventional membrane emulsification, this novel membrane emulsification could remarkably improve the size distribution of PLGA microspheres. The processing conditions, stirring rate, the stabilizer concentration, the PLGA concentration and the dispersed phase flow rate, were optimized to fabricate PLGA microspheres with controllable sizes and narrow size distribution. The results showed that uniform-sized PLGA microspheres (size distribution coefficient Rspan<0.50) were successfully fabricated using 2 ?m microporous membraneunder the conditions of stirring speed about 300 r/min, the stabilizer concentration of 1.0%(?), the PLGA concentration of 60 mg/mL and the dispersed phase flow rate of 20 mL/h. The relative standard deviation was 1.99%, and the product repeatability was good.