Abstract: There were lots of problems during manual sampling in the coal preparation plant of Jining NO.3 coal mine such as high labor intensity,grave errors,lagging results.To improve the detection precision of commercial coal and reduce labor intensity,meanwhile,better control clean coal production,the coal preparation plant adopts on-line ash indicators.The coal quality deviation between testing result gotten by on-line ash indicator and laboratory result is large,to resolve this problem,the coal preparation plant takes a series of actions such as stabilizing the quality of blending coal and feeding content,adding two kinds of coal blending methods on integrated control interface of blending coal feeding,controlling conveyor belt running.After transformation,the coal preparation plant improves the coal quality and economic benefits,reduces the labor intensity.