Poly (lactide-co-glycolide) (PLGA, LA/GA = 80/20) with different L-lactide and D-lactide molar ratio (L-LA/D-LA = 1.0∼0.5) has been synthesized, and electrospun into nanofibrous membranes. The obtained copolymers were characterized by 1HNMR, Polarimeter, GPC and DSC. The relationship between the contraction of the membranes and the L-LA/D-LA ratio of copolymers has been investigated through DSC, SEM and XRD. The results indicated that with the L-LA/D-LA ratio decreasing, the crystal fragments in copolymer decreased significantly even disappeared; meanwhile, the contraction of the membranes in PBS at 37 °C increased. The mechanism of the contraction of electrospun PLGA membrane during incubated is proposed based on the present results.