Abstract: The flame retardant epoxy compounds were prepared by mixing phosphoheterophene-borate molecular hybrid (ODOPB-Borate) with organic modified montmorillonite (OMMT) and SiO2,the synergistic effect of silicon-containing halogen-free flame retardants consisting of OMMT, SiO2 and ODOPB-Borate on the flame retardant performance of epoxy resin was investigated by means of thermogravimetric analysis, limiting oxygen index (LOI) and cone calorimetry. The results indicated that a combination of OMMT, SiO2 and ODOPB-Borate could effectively improve the flame retardant effect on epoxy resin. When 4 wt% of binary-combined flame retardant was incorporated at the OMMT/ODOPB-Borate or SiO2/ODOPB-Borate mass ratio of 1/7, the resulting epoxy compound achieved an LOI of 38.5 vol%~38.8 vol% as well as a UL 94 V-0 classification in the vertical burning test. Based on the experimental results in this work, the introduction of OMMT and SiO2could reduce the heat release rate of epoxy/ODOPB-Borate compounding system, improve their barrier protection, and optimize the distribution of flame retardant effect in the gas phase and condensed phase. These results confirmed a synergistic flame retardant effect between OMMT, silicon dioxide and ODOPB-Borate.