Objective To explore the molecular mechanism of methionine starvation induced apoptosis in gastric cancer cells. Methods The expression of programmed death ligand-1 (PD-L1) in gastric cancer tissues was analyzed by the cancer genome atlas (TCGA) database. The gastric cancer AGS cells and the gastric cancer cells treated with siRNA that inhibit the expression of PD-L1 (siPD-L1) were cultured with ordinary medium and methionine-starved medium. According to the treatment method, they were divided into control group, methionine starvation treatment group, siPD-L1 treatment group, and methionine starvation combined siPD-L1 treatment group. The cell viability of gastric cancer was detected by cell counting kit 8, the apoptosis of gastric cancer cells was detected by acridine orange/ethidium bromide double staining, and the apoptosis rate of gastric cancer cells was detected by flow cytometry. The expression levels of PD-L1, B-cell lymphoma-2 (Bcl-2), B-cell lymphoma-2-related X protein (Bax) and Caspase 3 were detected by Western blotting analysis. Finally, the relationship between PD-L1 and Bcl-2 anti-apoptotic protein family (Bcl-2 related protein A1[BCL2A1], myeloid cell leakemia 1[MCL1], BCL2, and Bcl-2 like 1[BCL2L1]) was analyzed by starBase database. Results PD-L1 was highly expressed in gastric cancer tissues (P<0.01), and the expression of PD-L1 was correlated with G grade of gastric cancer (P<0.01). Methionine starvation and siPD-L1 significantly decreased the survival rate of gastric cancer cells (P<0.01), promoted apoptosis (P<0.01), inhibited the expression of PD-L1 and Bcl-2 (P<0.05), and up-regulated the expression of proapoptotic proteins Bax and Caspase 3 (P<0.01). The effect of methionine starvation combined with siPD-L1 was even stronger (P<0.05). There was a positive correlation between PD-L1 and Bcl-2 anti-apoptotic protein family (P<0.01), indicating that PD-L1 is a key anti-apoptotic gene. Conclusion Methionine starvation can induce gastric cancer cell apoptosis by inhibiting the expression of PD-L1, downregulating the expression of anti-apoptotic protein Bcl-2 and up-regulating the expression of Bax and Caspase 3.