Abstract: The grafting reaction of polylactic acid(PLA)with maleic anhydride(MA)using 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as the initiator was investigated in this paper. Effects of reaction temperature, reaction time, dosage of initiator, and the amount of MA on the grafting degree were examined, and the suitable grafting conditions were determined as follows: reaction temperature 95℃, reaction time 3 h, the dosage of initiator 1%. The compatibility of a MA grafted PLA with starch composite was compared with a PLA with starch composite through differential scanning calorimeter(DSC), water absorption and SEM. The result showed that the MA grafted PLA with starch composite has the lower glass transition temperature and lower water absorption compared with a PLA with starch composite. That proved the compatibility was improved. The SEM also showed that the compatibility was improved obviously.