An underwater building defect detection method based on an autonomous navigation technology comprises the following steps: S1, based on two-dimensional map information of a given water area, carryingout full-coverage path planning on a to-be-detected water area through a full-coverage path planning traversal algorithm; S2, realizing autonomous navigation of the ROV in a three-dimensional underwater space through a depth setting control system, an attitude control system, a motion control system and a short baseline acoustic positioning system; and S3, performing defect detection and identification determination on the underwater building through ultrasonic imaging and an underwater camera system. According to the method, the autonomous navigation technology and the ROV are combined, and the control burden of remote manual control is reduced. Meanwhile, the definition of collected images is improved through the combination of the ultrasonic imaging technology and the underwater camerashooting technology, and the defect detection accuracy is improved.