Abstract: The risk factors of commercial medical insurance losses are investigated in this paper. We conduct an empirical analysis by fitting the Gamma generalized linear model to a commercial medical insurance's claims data. The result indicates that among the many candidate risk factors of medical insurance losses, the days of hospital stay, the hospital levels, the area where the insurance business is applied and the insurance level are significant. On the contrary, the gender and age are insignificant. Finally, some suggestions are presented, which we believe to be helpful for future medical insurance's operations and management.