Abstract: A new type of scanning device is designed for the critical preparation of ultrasonic testing of reactor pressure vessels, the calibration of ultrasonic probes. It mainly realizes stable clamping and smooth driving of the ultrasonic probe, and can accurately determine the moving position of the probe on the calibration test block, adjust the pressure of the probe on the surface of the test block and measure the pressure value. The device can be applied to different types of calibration test blocks to serve ultrasonic testing of pressure vessels. This paper focuses on the analysis of the structure, working principle and design points of the scanning device;the test was carried out with the designed scanning device, and good detection results were obtained.