Abstract: Polylactic acid modified by ethylene glycol was synthesized via melt polycondensation by using lactic acid (LA)and ethylene glycol (EG) as starting monomer material directly and characterized with intrinsic viscosity, FT-IR and DSC. The influences of different synthetic conditions including kinds and quantity of catalyst, time and temperature of melt copolycondensation, and different molar feed ratio were discussed in detail. Under the conditions of molar feed ratio of EG to LA 3∶100,amount of catalyst Sn(Otc)2 0.5(wt)%, polymerization temperature 170℃ and pressure 0.095MPa, polymerization time 8h the maximum of the as-prepared polymer was 16374, degradation performance of the products were improved, and maintained good water affinity performance. With the increase of the molar feed ratio of EG, its intrinsic viscosity, and glass-transition temperature decreased gradually.