The present study was conducted to investigate effects and mechanisms of action of phenolic alkaloids ofMenispermum dauricum (PAMD) on gastric cancer in vivo. In vitro, cell apoptosis of human gastric cancer cellline SGC-7901 was observed using fluorescence staining. In vivo, a mice model was constructed to observe tumorgrowth with different doses. Cell apoptosis was examined using flow cytometry and K-RAS protein expressionusing Western blotting. The mRNA expression of P53, BCL-2, BAX, CASPASE-3, K-RAS was examined byreal-time PCR. PAMD significantly suppressed tumor growth in the xenograft model of gastric cancer in a dosedependentmanner (p<0.01). Functionally, PAMD promoted cell apoptosis of the SGC-7901 cells and significantlyincreased the rate of cell apoptosis of gastric tumor cells (p<0.05). Mechanically, PAMD inhibited the expressionof oncogenic K-RAS both at the mRNA and protein levels. In addition, PAMD affected the mRNA expression ofthe cell apoptosis-related genes (P53, BCL-2, BAX, CASPASE-3). PAMD could suppress gastric tumor growthin vivo, possibly through inhibiting oncogenic K-RAS, and induce cell apoptosis possibly by targeting the cellapoptosis-related genes of P53, BCL-2, BAX, CASPASE-3.