Ultrasonic flaw detection device for underwater pipeline

The invention discloses an ultrasonic flaw detection device for an underwater pipeline, which comprises a single-degree-of-freedom mechanical arm, an ultrasonic flaw detection module and a main control module, wherein the single-degree-of-freedom mechanical arm and the ultrasonic flaw detection module are annular and are connected through thread engagement. Through a control instruction of the main control module, the flaw detection device can carry out surrounding fixation and nondestructive flaw detection on the underwater pipeline, that is, the main control module sends out a suction instruction to control the mechanical arm to realize suction of the underwater pipeline; an inspection instruction is sent out, the ultrasonic flaw detection module is controlled to achieve forward and reverse flaw detection operation processes of the underwater pipeline, and pose information of a phased array ultrasonic probe in the flaw detection operation process is recorded; and the main control module realizes high-precis