Abstract: In this paper, phased array ultrasonic high frequency guided wave is used to test the small diameter pipe. The detection ability of phased array ultrasonic high frequency guided wave is verified by comparing the corrosion pit and perforation defect simulated by flat bottom hole and through hole on the pipe used for small diameter pipeline. The experimental results show that phased array ultrasonic high frequency guided wave testing has the characteristics of image display, wide coverage and high detection efficiency. It can realize the detection of corrosion pits or perforation defects. It is a feasible nondestructive testing method for small diameter pipes.