Abstract: Aluminum phenylphosphinate (AlP) was synthesized by a co-precipitation method. A series of PLA/AlP composites were then prepared by melt blending, and the effect of AlP content on the thermal stability, flame retardant performance and combustion properties of the composites were investigated by thermogravimetric analysis, limiting oxygen index (LOI), vertical burning experiments and microscale combustion calorimeter (MCC). The results indicated that the incorporation of AlP enhanced the flame retardancy of PLA-matrix composites effectively, and the composites achieved a UL 94 V-0 classification as well as an LOI of 25.6 vol %. Thermal analysis showed that AlP improved the degradation temperature and residual char of the composites. MCC measurements demonstrated that the peak of heat release rate and the total heat release presented an increase at first and then decreased with an increase of AlP content.