A cyclic phosphate flame retardant named DOPC-THPE was synthesized from neopentyl glycol, phosphorus oxychloride and 1,1,1-tris(4-hydroxyphenyl)ethane (THPE). The chemical structure of DPPC-THPE was identified via FTIR, 1HNMR, 13CNMR and 31PNMR. TGA curves indicated that DPPC-THPE had good charring performance and thermal stability, with a char of 35.9% at 700 ℃. Then the product was added to polypropylene to improve its flame retardancy. Limited oxygen index (LOI) and vertical burning tests were utilized to investigate the flame retardancy of the samples. The results suggested that when the loading of DOPC-THPE was 30.0 wt%, the LOI value of PP composite could be increased from 17.5 to 25.0% and V-1 rating could be achieved.