Under complex sea conditions，there are many kinds of equipment available for 3D detection and accurate positioning analysis of underwater hydraulic structures. However，the reliability and accuracy of the detection need to be further analyzed and verified. Combining with Guangdong Jieyang Petrochemical Crude Oil Terminal Project，we adopt the multi-beam echo-sounder system and the underwater 3D real-time sonar system，and build model with the point cloud data. The data collected by the two systems are integrated and processed，and the coordinate and elevation of the building are accurately analyzed. The multi-beam echo-sounder system can be used for measuring the absolute coordinates of underwater structures，and the real-time 3D sonar system can obtain accurate model image of the target object. Integrating and processing the two kinds of data，we can accurately analyze the position and state of the object by the visual method. This method can be used for the harbor and wharf maintenance，underwater building inspection，and provide an effective detection and positioning method and visual tools for the reconstruction and restoration of old wharves.