Abstract: Conventional ultrasonic NDT method is quite incompetence for the surface fatigue crack testing of in service rotary shaft. Considering the formation mechanism of the surface fatigue crack in rotary shaft and the propagation character of ultrasonic creeping wave in media, ultrasonic creeping wave was employed to the surface fatigue crack detection of in service rotary shaft. An experiment was carried out on a certain type of stepped rotary shaft for the testing of surface fatigue cracks. The result revealed that, this method was simple and efficient for the surface fatigue crack testing of in service rotary shaft, and it could be applied for the routine testing of in service rotary shaft.