Novel organic/inorganic epoxy hybrids containing DOPO and silica were synthesized by in situ polymerization. The sol-gel and thermocuring processes are employed to incorporate the DOPO-VTS into the structures of epoxy resins, resulting in the formation of organic/inorganic epoxy hybrids. The LOI of the EP/DOPO-VTS hybrids increased from 22.5 to 32 and the hybrids with 15 wt.% DOPO-VTS can reach V-0 rate in UL94 vertical test. The thermal and combustion properties of the hybrid resins were investigated by thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC) respectively, demonstrating that the incorporation of organic/inorganic materials can improve the flame retardancy of epoxy resins. Based on the thermogravimetric analysis/infrared spectrometry (TG-IR) and the direct pyrolysis/mass spectrography (DP-MS) results, the combustion products of the hybrids at different temperature were fully evaluated, indicating that the DOPO and its derivates are released at low temperature as well as high temperature during the decomposition process. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.