Three new isopimarane diterpenes and one new nor-triterpenes, along with five known diterpenes were isolated from the whole areal part of Ephorbia alatavica Boiss. The structures of the new compounds (1-4) were determined based on extensive spectroscopic analysis, including HR-ESIMS, 1D and 2D NMR data. A plausible biosynthetic pathway for new compounds (1-4) were hypothesized. All isolated compounds were screen for cytotoxicity activity against MCF-8, HeLa and A549 cell lines in vitro by MIT assay. New compound 1 and known 9 showed potential cytotoxic activities with IC50 values of 15.327 mu g/mL, 23.066 mu g/mL against MCF-8 cell lines, compoundl showed noteworthy cytotoxic activity with IC50 13.033 mu g/mL against A549 cancer cell line. New compounds 2, 4 and 4 showed moderate cytotoxic activities three human cancer lines with IC50 value around 50 mu g/mL, which compared with positive control doxorubicin (DOX).