Abstract: Density of feed pulp is an important factor in flotation process.The traditional ray analytical methods fail to find widespread application for density measurement due to restriction of usage while the densimeters of the differential version generally suffer from the drawbacks of being low in measuring accuracy.For tackling the problem currently encountered in determination of flotation feed pulp density in coal preparation plant,a noval optical transmission method is proposed.The paper presents an introduction to the structure,working principle,electronics desigh of the desimeter proposed and the method for its calibration.The density of the pulp can be calculated based on the remanence of the infrared light after passing through pulp and ist relationship to corresponding slurry water density,and in line with the law of photosorption.As evidenced by test on site after calibration,the measured result is much higher in objectivity truthfulness and accuracy than before,well meeting the requirements of coal preparation plant.