Abstract: The blades work under the conditions of high altitude and all weather, bear large load and bad operating environment. Therefore, the nondestructive testing of wind turbine blades should be carried out during manufacturing to help ensure blade integrity. This paper introduces a NDT method of wind power blades using low frequency phased array ultrasonic technology, and the detection results of some typical defects. The phased array ultrasonic image signal of common defects is analyzed. It can be seen that phased array ultrasonic testing is an effective method to inspect the quality of blade shell and shell-beam bonding.