Abstract: In response to the demand for ultrasonic nondestructive testing of grid rudder welds, a device suitable for ultrasonic testing of grid rudder welds was developed based on the development of array ultrasonic hosts, transducers, and imaging software, in order to solve the problems of low reliability, long cycle, and low system maturity in manual scanning and defect assessment. This device met the automatic testing requirements of grid rudder welds. The device used PLC (Programmable Logic Controller) as the control core and GSKLink communication protocol to control the robot and servo motor. Based on the structure of the grid rudder weld seam, an automated process flow was designed to achieve target automation detection. Through actual operation of the device and its application in production, it was proven that the device can meet the automatic ultrasonic testing requirements of grid rudder welds, greatly improving the production efficiency of grid rudder.