Cinobufacini is an aqueous extract of Bufo bufo gargarizans Cantor dried skin, which has been widely used for cancer therapy in China. So far, its active components are still not very clear. In previous reports, bufadienolides with low-concentration were usually studied because of their anticancer effects. However, the high polarity constituents in cinobufacini are less investigated. The present study found that more than 50% contents of cinobufacini were water-soluble peptides. Then, in vitro anticancer experiments were carried out, including human stomach cancer cell lines BGC823 and MCG803, human colon cancer cell lines DLD-1 and HT-29, and human pancreatic cancer cell line MIAPACA-2. The IC50 for these cell lines model were ranged from 25-123 microgmL(-1). The results indicated that these peptides showed similar activity with cinobufacini injection. As a conclusion, this study provides a new and further understanding of anticancer components in cinobufacini injection.