Abstract: After the operation of water ring vacuum pump for a long time in coal mine, it is influenced by the mechanical vibration, and causes axial movement; the clearance between the impeller and the side cover changes, which not only increases the impeller rotating friction resistance, also reduces the pump body of the vacuum degree, and seriously influences efficient run of gas extraction system. Using feeler to measure clearance of water ring vacuum pump side cover, and with the aid of jacks and axial jackscrew to adjust the gap to a reasonable interval, at the same time, the replacement process and method of tapered roller bearing were described in detail.