Study focused on the magnesium alloy hot rolling process. A method was proposed to determine the friction coefficient in process through the comparative analysis of finite element analysis result and experimental data. Mathematical model for solving the friction coefficient was established, combining with multi-parameters of the rolling process: rolling temperature, rolling speed and reduction rate. Based on calculation model of rolling force and temperature distribution along the contact region in hot rolling of AZ31B magnesium alloy in previous research, rolling force prediction model was optimized and reconstructed considering the normal pressure and friction stress comprehensively. The contact friction stress and its influence on rolling force with an approximate percentage of 4.36% was defined.