In the paper, the thermo-properties of unsaturated polyester resin (UPR)/epoxy resin(E51) composites through reactive blending method were studied by DSC. The experimental results showed that, when the amount of E51 in UPR/E51 composites reached to 2wt%, the mixture take place glass transition at 84°C which higher than that of pure UPR 15%. When the amount of E51 reached to 10wt%, the mixture take place two glass transition at 59°C、104°C respectively. The morphologies of the mixtures were investigated by SEM, and the curing process of UPR/E51 was traced and investigated by FTIR.