Abstract: The study aims at solving the problem of gas overrun in super long fully mechanized caving face, obtaining the reasonable parameters of the mining process and improving the working efficiency. Taking N2015 working face of Yuwu Coal Industry as the research object, a mathematical model of gas diffusion in fully mechanized caving face is established on the basis of the Fluent modeling software, a numerical study is carried out on the parameters, which can result in the gas accumulation, such as gas velocity, the recovery rate of surrounding rock, gas emission and other factors. It is concluded that if the following conditions can be satisfied, i.e. average wind speed is 3 m/s at working face, coal seam gas desorption is less than 4 m³/t, the speed of working face is not greater than 4.8 m/d, the coal mining rate is more than 95% and the surrounding gas emission is less than 10 m³/min, the best effect of preventing gas accumulation can be achieved.