The invention relates to an automatic detection system of a ship draught depth based on the single-beam sonar array scanning technique. The automatic detection system comprises a single-beam sonar primitive array, a sonar signal processor and a back stage master control system. The single-beam sonar primitive array is installed on an approach channel cross section so as to form a draught depth detection door device. The single-beam sonar primitive array is a combination of a set of single-beam transducers. The sonar signal processor is used for performing sequence collecting, signal amplifying, filtering, analog-digital conversion and DSP processing on all the transducers, and a formed digital signal is transmitted to the back stage master control system through the RS485 protocol. The single-beam sonar primitive array is connected with the sonar signal processor arranged on the shore through a watertight cable. The back stage master control system comprises a master control computer and a power supply unit. An upper computer software system is operated on the master control computer. The automatic detection system of the ship draught depth based on the single-beam sonar array scanning technique has the advantages of being small in investment, easy to install and maintain, simple, fast and efficient in measuring process and high in measuring precision.