Abstract: The coal slurry ash detection is a nodus to on line material goods analyze in the coal preparation plant. Furthermore the ash control of the flotation concentrate can’t be set foot in it. This paper discusses the fundamental principle and the structure of the coal slurry detector, the composition and the work principle of the multi slurry ash detecting system, the basic struture and the working model of the computer control system of the coal flotation, and the using situation in Huaibei Coal Preparation Plant.