The invention relates to an automatic ship draught detection system based on the multi-beam side-scan sonar technology. The automatic ship draught detection system comprises an underwater sonar scanning subsystem, a sonar signal processing subsystem and a master control subsystem. The underwater sonar scanning subsystem comprises a sonar transducer and a rotating motor, wherein the sonar transducer is provided with a 360-degree rotating shaft, and the rotating motor is used for driving the sonar transducer to rotate. The sonar signal processing subsystem comprises a watertight electronic cabin and a digital signal processing module located in the watertight electronic cabin, and data and command transmission between the sonar signal processing subsystem and the master control subsystem is carried out through a watertight cable. The rotating motor of the underwater sonar scanning subsystem is fixed in the watertight electronic cabin and connected with the digital signal processing module. The master control subsystem comprises a master control computer and a power supply unit, and display and control software of the automatic ship draught detection system operates on the master control computer. The automatic ship draught detection system has the advantages of being small in investment, easy to install and maintain and high in measuring accuracy, and the measurement process is convenient and fast to carry out and efficient.