The influences of molecular weight on electron beam (EB) curing in epoxy resins were studied. The rate of radiation reaction in epoxy resin systems decreases with the increasing molecular weight. Under the low radiation dose, the curing thickness and curing degree is small for samples with high molecular weight. The effect of molecular weight decreases with the increasing radiation dose. The glass transition temperature (,T,g) and the storage modulus (,E,＇) are under the control of curing degree in samples, and the molecular weight will play a role on the samples with similar curing degree. After heat treatment, the ,T,g and ,E,＇of epoxy resins cured by radiation will increase. The molecular weight is directly associated with effect of heat treatment.