Piperazine pyrophosphate (PAPP) is an environmentally friendly flame retardant, but its flame-retardant efficiency in polylactic acid (PLA) is relatively low. Usually, 25% PAPP is required to reach the UL-94 V0 rating. In this paper, a piperazine pyrophosphate containing substituent group (H-PAPP) was used to improve the flame retardancy of PLA, and glycidyl isocyanurate (TGIC) was used to regulate its mechanical properties. The results show that PLA containing 3% H-PAPP achieves UL-94 V0 rating. In nitrogen atmosphere, H-PAPP reduces the 5% degradation temperature (T_5% ) of PLA, while in air, it increases T_5% of PLA. However, the increase in the char residue of PLA is not significant. The cone calorimetry test results show that although H-PAPP reduces the total heat release, the peak heat release and smoke release are increased. In addition, H-PAPP reduces the tensile and impact strength, while TGIC improves the mechanical properties of PLA by chain extension reaction.