In order to locate the cracks of the expensive metal rotating body more accurately, according to the principle of eddy current detection, a kind of crack detection device for the surface of metal rotating body was designed. In the detection device,the method that the eddy current sensor was moved linearly and the rotating body was rotated was used to detect the outer surface of the rotating body.The detection device was mainly composed of the transmission, transmission structure, eddy current sensor, lifting adjustment mechanism and coordinate recording structure. The output data were denoised, displayed and stored by data transfer among eddy current sensors,data acquisition cards, computers. The device can be used to detect and store the surface cracks of the rotating body with a large diameter, which provides convenience for the crack turning work and has reference value for other designers.