With the large-scale construction and promotion of smart substations, the application of digital equipment and testers is increasing significantly. Thus the test and calibration of digital signal accuracy of a power system have become key issues. At present, the testing methods of digital signal accuracy in a power system are unprofessional, inconvenient and inaccurate. This affects the efficiency and quality of test and calibration, and is not conducive to the promotion and application of digital equipment in smart substations and long-term quality and safety. To solve this problem, a digital signal test and calibration device for a power system is researched and implemented. From the three aspects of theoretical value, time scale and algorithm traceability, the full performance index of digital signal accuracy can be tested and calibrated. Test and engineering verification show that the function and anti-interference results meet the standard and application requirements, and improve the efficiency and quality of digital signal test and calibration.