Abstract: With the overall requirements of carbon neutrality and peak carbon emissions, the development of renewable energy power is accelerating rapidly, and its consumption and transmission are becoming increasingly important. Flexible direct current transmission, as a new generation of direct current transmission technology, has been fully developed and widely applied in engineering due to its advantages of high transmission efficiency, strong flexibility, energy conservation and environmental protection, which can improve the stability and reliability of the power grid. The key component of flexible direct current transmission is the sub module control board of the converter valve, namely the SMC board, which is particularly important for its correct and stable operation. To achieve automatic testing of SMC boards and verify their hardware functionality, a SMC board testing system is proposed. This system consists of a debugging device, testing fixture, programmable source, barcode scanner, and the SMC board. The SMC board testing system is used to automatically control the testing process through the debugging device. The testing is efficient and convenient, and can be applied to plugin board production testing in the factory and on-site maintenance testing in engineering.