D,L-lactide was prepared from D,L-lactic acid by means of polymerization and depolymerization at low vacuum level. Morpholine-2,5-dione (MD) was synthesized from the cyclization of chloroacetyl glycine which was made from chloroacetyl chloride and glycine in the basic condition. A novel copolymer (PLAMD) with D,L-lactide (D,L-LA) and morpholine-2,5-dione (MD) was synthesized using stannous octoate as initiator, and characterized with FT-IR and 1HNMR. The biocompatibility of PLAMD and PLA was investigated by MTT and microscope. The results show that amino acid is introduced into PDLLA main chain. PLAMD has better cell affinity than PLA, so it is a promising biomaterial.