An efficient phosphorous flame retardant rich in aromatic rings was synthesized and introduced into epoxy resin. The flame retardant properties of the resultant composites were studied, and the results were compared with those of 5 wt% tris(bis(4-((diphenoxyphosphoryl)oxy)phenyl)methyl) benzene-1,3,5-tricarboxylate (DHPP-OH-BAC), 10 wt% DHPP-OH-BAC and 15 wt.% DHPP-OH-BAC samples. The results showed that the 15% DHPP-OH-BAC sample had the best flame retardancy effect, a limiting oxygen index of 33.6%, and UL-94 V-0 level. A cone calorimeter experiment showed that the addition of flame retardant can significantly reduce the amount of smoke and heat. Macroscopic digital photographs, scanning electron micrographs and thermogravimetric analysis results further revealed that DHPP-OH-BAC can exhibit high char yields. The flame retardancy mechanism of DHPP-OH-BAC was preliminarily shown by pyrolysis-gas chromatography-mass spectrometry analysis. The test results show that a high-efficiency phosphorous flame retardant rich in aromatic rings was successfully developed. POLYM. ENG. SCI., 59:E406-E413, 2019. (c) 2019 Society of Plastics Engineers