Abstract: A novel single molecular intumescent flame retardant-aluminum Pmethylpropionanilide methyl phosphinate（Al（PMPMP））was synthesized by 2-methyl-2，5-dioxo-1，2-oxaphospholane（OP）through a three-step reaction. The target product was characterized by Fourier transform infrared spectroscopy（FTIR）and hydrogen nuclear magnetic resonance（¹H-NMR）. The limit oxygen index （LOI）of polylactic acid（PLA） increased from 17. 6% to 28. 5% when adding Al（PMPMP）with a mass fraction of 15%，and the vertical burning test could pass the UL94 V-0 rating. Microscale combustion calorimeter results demonstrated that Al（PMPMP） exhibited superior performance in inhibiting heat release rate for PLA. TG-FTIR combination analysis displayed that Al （PMPMP） could effectively reduce the release of flammable gases during the thermal decomposition process of PLA. In addition，scanning electron microscopy（SEM） analysis confirmed that the flame retardant composites showed obvious foam expansion after combustion， forming a carbon layer with a dense surface and a porous inner layer. In summary，Al（PMPMP） achieved benign synergistic flame retardancy for PLA in the gas phase and condensation phase.

Key words: single molecular, intumescent, flame retardant, polylactic acid