Abstract: The activity of curing reaction of modified rosin based alicyclic epoxy resin with modified methyl hexahydrophthalic anhydride was investigated by thermal analysis and gelatin time determination. The curing process and reaction mechanism of this epoxy resin/modified liquid anhydride system were studied by qualitative analysis of FT-IR spectrum and quantitative determination of curing degree. It was shown that curing reaction of this kind of epoxy resin with modified liquid anhydride was an exothermic reaction, and the reaction enthalpy determined by DSC method was 272-335 J/g. The gelation time of this epoxy resin with modified liquid anhydride was related to the chemical structure and the composition of epoxy resin, curing temperature and accelerator. The reaction process and curing mechanism were basically identical to the curing reaction of bisphenol A epoxy resin with anhydride in the presence of accelerator.