Abstract: In order to improve the flame retardancy of oil plasticizer and develop high value-added products using crude glycerin from by-product of diesel oil as starting materials, a novel P-containing soybean-oil-based fire-retardant plasticizer(DOPO-EAPFAE) was synthesized using crude glycerin, oleic acid and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as raw material through polymerization, esterification, epoxidation and ring opening reaction.The structure was verified by Fourier transform infrared (FT-IR) spectrometry and nuclear magnetic resonance spectroscopy.Thermo-gravimetric behavior and flame retardant properties were evaluated by thermal gravimetric analysis, oxygen index test and vertical burning test.When the amount 60% of phthalic acid dioctyl ester (DOP) was replaced by DOPO-EAPFAE in PVC blends, PVC blends still has good mechanical properties.The limiting oxygen index (LOI) of the blends increased from 21.3 to 28.7, and flame retardant level reached V0 grade.This indicated that the product can effectively improve the flame retardancy of PVC blends.The plasticity and flammability of DOPO-EAPFAE was better than tris(chlorisopropyl) phosphate(TCPP).Comparing to small molecular flame retardant tris(1-chloro-2-propyl) phosphate(TCPP), flame retardant of DOPO-EAPFAE was not only superior to TCPP, but also exhibited better thermal stability.