Epoxy – Polysulfide copolymers without or with low amounts of epoxy in their structure have poor mechanical properties in oxidative curing system.To strengthen the mechanical properties of polysulfide elastomer inclusion of epoxy resin (Epon828) as hard segment was studied. FT-IR spectroscopy and rheometry were used to verify the formation of epoxy-polysulfide copolymer. Results obtained from DMTA showed that in different epoxy/polysulfide ratio, the epoxy-polysulfide copolymer had different glass transition temperature (Tg). Gel time and curing behaviors in various ratios of epoxy – polysulfide were investigated using Rheometer and Differential Scanning Calorimeter (DSC). With increasing polysulfide weight percent in epoxy - polysulfide copolymer gel time increased but the enthalpy of cure reaction decreased and the temperature corresponding to exothermic peak was shifted to the higher temperature. Results obtained from DMTA and SEM showed that phase separation of epoxy resin from the copolymer matrix took place