With the increase of coal mining depth and intensity, gas disaster prevention and control has become the key to coal mine safety production. In this paper, taking the S1305 fully mechanized mining face of Yuwu Coal Industry Company as the engineering background, the numerical simulation of different ventilation modes in the working face is carried out, and then the gas migration law in the goaf of the working face is analyzed. The simulation results reveal the monotonous variation law of gas concentration distribution in the goaf of ' U ' type ventilation, and the gas accumulates in the return corner of the goaf. The high gas concentration in the ' Y ' type ventilation goaf is located in the deep part of the goaf and the return air side, and the gas concentration distribution is C-type and S-type at different heights. The research results provide a theoretical basis for the mine to change from ' U ' type ventilation to ' Y ' type ventilation to solve the problem of gas overrun in the upper corner and return air flow of fully mechanized mining face.