Abstract: On the issue of the water ring vacuum pump impeller cavitation and blade fracture of the main engine and the small engine of the 350 MW unit in Inner Mongolia Jingneng Kangbashi Thermal Power Co., Ltd., combining with the working principle of water ring vacuum pump, put forward the transformation measures.Equip air ejector on the vacuum pump to increase the internal working pressure of the vacuum pump, thus eliminate the cavitation and improve the working environment of the impeller.The performance, operating current, noise level, cavitation condition, condenser vacuum and economical efficiency of vacuum pump before and after improvement are compared.The results of the comparison prove that the transformation efficiency is good.The transformation measure is also available for the similar transformation of other power plants.