Abstract: In order to perform nondestructive testing on the inclined joint surface of the whole turbine, based on the overall structural characteristics of the turbine, this paper designs and develops a set of ultrasonic imaging detection system with the same depth scanning. Based on the characteristics of the controllable deflection angle of the ultrasonic phased array, the phased array transmits sound waves, the curved surface probe receives the sound waves, and the automatic scanning device is used to scan the inclined plane of the turbine. After the received signal is acquired, the defect in the oblique joint surface is imaged with the characteristic of the amplitude of the signal. The test results show that the device can detect ultrasonic defects with diameters of 2 mm and 3 mm at the depths of 30, 50, 70, 90 mm beneath of the turbine oblique joint surface, and realize the accurate ultrasonic imaging detection of the defects of the whole turbine oblique joint surface at different depth positions.