Abstract: In order to improve working environment of underground coal miners and reduce emissions of pollutants such as NOx, CO, HC, etc., power and emission performances of a certain type of explosion-proof diesel under different air intake flow were studied according to working environment of explosion-proof diesel and emission regulations, and the appropriate air intake flow of explosion-proof diesel was determined. The test results show that reducing air intake flow will reduce power performance of explosion-proof diesel, and increase smoke slightly, but it will also reduce the emissions of NOx.