Abstract: Primary gastric cancer (GC) is one of the most frequently diagnosed cancers worldwide.The incidence of GC in male is approximately twice the incidence thereof in female. Before 60 years of age, the male-female ratio of GC incidence has no geographic and ethic differences, and rises with the increase of age. Studies of classic and molecular epidemiology have proved that the sexual dimorphism in GC is due to synergetic effects of various factors including chronic infection, dietary habit, gene mutation, genetic susceptibility, estrogenic effects and differences in lifestyle behaviors, etc. Studies on the above-mentioned factors can not only help clarify the carcinogenesis of GC, but also help improve the strategies of GC control and prevention, and reducing GC incidence subsequently.