Gastric cancer has a high incidence and mortality in the world, especially in China. The pathogenesis leading to the high heterogeneity of gastric cancer remains unclear. It is believed that TWSG1 is associated with a variety of tumors, but there are few studies related to gastric cancer. To investigate the biological significance of TWSG1, we evaluated the TWSG1 expression of the clinical samples and gastric cancer cell lines (BGC-823, MGC-803, and SGC-790) via stomach cancer tissue array, real-time PCR, and western blotting. Then, we used CCK-8 and flow cytometry to detect the function and mechanism of TWSG1 in gastric cell lines. The analysis showed that TWSG1 showed decreased expression in clinical samples and BGC-823, MGC-803, and SGC-7901 cells. And, overexpressed TWSG1 inhibited the cell cycle and proliferation, TWSG1 might influence the proliferation of SGC-7901 and MGC-803 by regulating the BMP signaling. However, the influence of TWSG1 on BGC-823 cell is not associated with the BMP signaling. In conclusion, all of our findings revealed that TWSG1 maybe serves as a tumor suppressor gene in gastric cancer and potential biomarker or therapeutic target for the diagnosis and treatment of gastric cancer.