A tetrafunctional epoxy resin was modified using CO2 fixation process in the presence of tetra-n-butyl ammonium bromide as catalyst. The unmodified tetrafunctional epoxy resin (UMTE) and CO2 fixated modified tetrafunctional epoxy resin (CFMTE) were cured by diethylenetriamine. A bifunctional glycidyl ether compound was used as a reactive diluent to control the viscosity of CFMTE. The activation energy of curing reaction was computed using the advanced integral isoconversional method. The activation energy, which depends on the conversion, was considerably changed due to the CO2 fixation process. The thermal stability parameters including the initial degradation temperature, the temperature at the maximum rate of weight loss (T (max)), and the decomposition activation energy (E (d)) were determined by thermal gravimetry. Dynamic mechanical thermal analysis measurements showed that the CO2 fixation decreases the T (g) of the epoxy resin. The surface morphology of UMTE and CFMTE were determined by scanning electron microscope. It is concluded that CO2 fixation reaction improves the properties of tetrafunctional epoxy resin.