The present invention discloses SPAG5 gene and its expression product that may serve as a molecular marker for endometrial cancer diagnosis and treatment. By detecting SPAG5 gene and its expression product in endometrial tissues of a subject, it is possible to judge whether the subject is afflicted with endometrial cancer or to diagnose whether the subject is in the risk of being afflicted with endometrial cancer. The study on proliferation, apoptosis and migration conditions of endometrial cancer cells cultured in vitro shows that it is possible to inhibit cell proliferation, promote cell apoptosis and inhibit cell migration by inhibiting the expression of SPAG5 gene, and results of the study show that the SPAG5 and its expression product are a potential drug target for treating endometrial cancer.