Abstract: Aiming at the issue that mass of CO emission from the gob area to 42221 working face in the Yujialiang Coal Mine, by the means of numerical simulation, the measure of the fan and air window jointed working for changing the pressure distribution along the wind path was studied to reduce the differential pressure at the ends of the working face, decrease the air leakage, and prevent the CO emission. According to the theory of ventilation dynamics, the principle of pressure balancing ventilation was analyzed, and the fluid mechanics software Fluent was used to simulate the distribution of leakage air, static pressure and the changes of CO concentration in gob area before and after the implementation of pressure balancing. The results showed that the differential pressure at the ends of the working face reduced significantly, and then made the air leakage and the concentration of CO in the working face greatly decreased after using the pressure balancing ventilation. It effectively resolved the problem of CO and other harmful gas emission to the working face.