Abstract: Due to poly(lactic acid) (PLA) was easy to burn and accompanied by serious droplet phenomenon, its application in many fields such as packaging, automotive, electrical and electronic industries were seriously limited. And in order to solve this problem, PLA was used as matrix and poly(2-10-hydrogen-9-oxa-phosphaphenanthrene hydroquinone phenyl phosphate) (POPP) was used as flame retardant. PLA composites with different contents were prepared via melting blending and hot-compression method. The flame retardant properties and smoke suppression of PLA composites were investigated by means of limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TG) and cone calorimetric test etc. The results show that the LOI of PLA composite with 4wt% POPP is 34.8%, and it reaches a UL-94 V-0 rating. Comparing with pure PLA, the smoke production rate and total smoke production of POPP/PLA-4 are respectively reduced by 85.83% and 77.65%, which dramatically improve the smoke suppression performance of PLA materials. Moreover, the results of microstructure of char residues after cone calorimeter and thermal degradation behavior analysis reveal that the excellent flame-retardant performance of PLA composites are followed a flame-retardant mechanism of gaseous phase at superiority. This is attributed to •PO and •PO₂ decomposed by POPP quenching •H and •OH. Otherwise, by promoting the intermolecular crosslinking of PLA, a continuous and dense carbon layer on the surface is formed, which improve flame retardancy of PLA composites.