Abstract: In order to solve the problem of the poor accuracy for the joint elongation fault detection,a method for coal mining conveyor beltijoint elongation calculating a nd fault detecting based on conditions Y difference was proposed. Using the conveyor belt X-ray images,theimage processing technology based on the conditions Y differe ntial algorithm was put forward to calculate the each docking slot elongationof the steel cord. One steel cord conveyor belt of Jincheng Anthracite Mining Group Wangtai Mi ne was tested,and the results showed thatthe method combining with the overall joint elongation calculating realized the integrated detection and judgment for the joint elo ngationfault and could be used for the coal mining conveyor belt safety protection and fault positioning accurately.