Thiirane is usually synthesized by epoxy resin, and there are considerable content of epoxy mixed in thiirane because of the poor yields. In this article, a novel separation method was used to get pure episulfide compound and epoxy compound from thiirane/epoxy resin synthesized in our lab. Furthermore, the perfect 1H NMR spectra of pure episulfide compound and epoxide compound were obtained. The quantitative analysis of content of epoxy groups in thiirane/epoxy resin was performed by using FTIR and was testified by 1H NMR. It was found that the analytical results of the conversion of epoxy groups by the two methods above coincided with each other well.