The safety DCS system is an important part of a nuclear power plant. The priority logic selection module (PLM), as the main interface between the safety-level DCS and the field drivers, is crucial in the safety-level DCS system. In an actual project, the PIO and priority function tests of more than 700 priority logic selection modules (PLM) of the safety-level DCS system were all completed through manual testing during the factory test phase. There were problems such as slow test progress and long test cycles. In order to solve the above problems, an automatic testing solution is proposed, and an automated testing device is designed based on NI platform hardware equipment and LabVIEW development environment. Through the functional performance verification of the test device, the verification results meet the requirements and meet the conditions for engineering application.