Abstract: For large detection error of single point ultrasonic ranging technology used in material flow detection of belt conveyor when coal distributed unevenly or was big, a material flow detection method of belt conveyor based on multi points ultrasonic counter ranging technology. The method can calculate approximate sectional area of material by locating multi points on surfaces of material and belt, so as to get material flow according to running speed of belt conveyor. The test result shows that the method has smaller detection error than the single point ultrasonic ranging technology under the condition of big coal with uneven distribution.