Abstract: A number of thermosets of liquid chloroprene-hydroxyethyl methacrylate copolymer(CP-co-HEMA) modified epoxy resin were prepared. The mechanical properties of theresin were improved after modification. The shear strength of the modified system began to drop when CP-co-HEMA content is more than 30%. The data of the experiments carried out by monitoring with IR and Curelastometer indicatad that during the curing the etheri fication of primary hydroxyl groups of CP-co-HEMA with epoxy groups and the selfpolymerization of epoxy groups occur simultaneously and the etherification appeared to bring about an improvement in the mechanical properties of the thermosets thus obtained.The effects of the curing conditions and CP-co-HEMA content on morphology were studied.It was found that high temperature is in favour of microphase separation and when the curing temperature is low thermodynamic diffusion of the system is a dominant factor.