Abstract: The coal slime water deposition interface is an important technical parameter to describe the working state of the thickener. It is of great significance to guide the parameter control of slurry flocculant dosage. In this paper,the object is the rule of the distribution of coal slime concentration and particle size in the thickener of shendong coal preparation center coal preparation oil preparation plant. 14 points from 100 mm to 13 100 mm and 16 positions from 100 mm to 4 900 mm were selected along radial equidistance,and 195 sampling points were set altogether. The results show that the concentration of coal slime water in the thickener is higher as it goes down from the surface,the concentration of coal slime below 3 600 mm increases sharply and there is fluctuation. The concentration of coal slime water along the radial horizontal distribution of the thickener changes independently of the sampling radius. Ultrasonic testing platform is designed and manufactured by ultrasonic detection principle,the operating frequency of ultrasonic is set as 66 MHz. When ultrasonic wave propagates in coal slime water,the ultrasonic wave would attenuate affected by coal slime in coal slime water. This phenomenon was used to detect the concentration of coal slime water at different depths in the thickener,thus the depth of coal slime water deposition interface in the thickener was calculated. The results show that there is a good linear relationship between the concentration of coal slime water and the difference of ultrasonic transmitting and receiving frequency. The height of fresh water layer during the production and shutdown of the thickener was tested respectively,and the results were compared with the artificial detection of the height of the fresh water layer. The experiment shows that the index difference value between ultrasonic testing platform and manual testing is 46-57 mm. It can replace manual test and realize automatic detection of deposition interface parameters of thickener. This test platform provides an important basis for automatic control of the subsequent sedimentation process of coal slime water flocculation.