Ball mills play a vital part in affecting the economic and technical index and ore dressing cost in the process of beneficiation.The motors of the ball mills in the concentrator of Canzhuang Gold Mine start using frequency sensitive rheostat and liquid resistance starter,but the starting current is strong,the electrical spare wearing is severe and the grid impact is intense.In view of those problems,the frequency converter is used to control the starting and shutting and rotation speed of the ball mills and technical renovation is carried out.Onsite industrial application shows that speed adjusting control by the frequency converter has achieved smooth softer starting and shutting of ball mills and the cost is greatly reduced,energy saving is evident,safety is imporved,grinding quality is greatly improved,more than 200 000 yuan maintenance fee and more than 1 million yuan power charge are saved annually.