With the aim of supporting the folk applications of Euphorbia fischeriana, a phytochemical study was performed, which led to the discovery of 9 compounds, including three new ones (1-3) and six known ones (4-9). Their structures were determined by 1D, 2D NMR, and HRESIMS analysis. In the cytotoxic assays on Hep-3B cell line, 2 showed stronger inhibitory effects (IC50 8.1μmol/L) than that of positive control, and 1, 8 and 9 also gave inhibitory effects in a certain degree with IC50 values of 12.5, 12.0 and 18.7μmol/L, respectively. While on A549, the cytotoxic activities of 1 (IC50 11.9μmol/L) and 8 (IC50 9.4μmol/L) were superior to that of 5-Fu, and those of 4 and 9 were moderate with IC50 values of 28.2 and 29.8μmol/L, respectively. In addition, both petroleum ether and dichloromethane extracts showed cytotoxic activities with different degree, while n-butanol extracts had no effect. The results clarified that the low-polarity fractions of E. fischeriana, including triterpenoids, abietane and tigliane-type diterpenoids might be the potential bioactive ingredients which will exert strong antitumor effects.