Safety accident is caused by super draft when the ships pass the lock,ship lift and other navigation facilities.The common draft check methods have disadvantages,and cannot satisfy the check requirement.Combining with the diffraction principle of the ultrasonic wave,we design a draft check system based on the single-beam ultrasonic arrays in side-scan setting，introduce the composition and function of this system in detail,and install and test the system in the Gezhouba ship lock.The results show that this system has the advantages of strong adaptability of muddy water,easy installation and convenient maintenance,can effectively detect the draft of the ship.The standard deviation between measured draft depth and validation data is less than 0.086 m.This system has certain forewarning function to the passing ships.