Abstract: In the process of verifying relay protection devices, ignoring the influence of harmonic factors can lead to a decrease in the performance of the verification method. To solve this problem, a verification method for relay protection devices in main grid substations based on differential Fourier algorithm is proposed. The differential Fourier algorithm is used to perform differential processing on the input current of the relay protection device, and then the differential signal is Fourier transformed. Under the action of the dynamic window function, the dynamic characteristic curve of the relay protection device is set. On this basis, calculate the response error of the relay protection device under multiple harmonic states and determine the characteristic coefficients. Set the verification value for the protection action of the relay protection device, combined with the set characteristic coefficient, construct the verification function for the relay protection device, and achieve the verification of the action status of the relay protection device. The experimental results show that the designed verification method has an overlap of 96.72% between the verification results and the actual results in practical applications, and the misoperation rate of the relay protection device after verification is 1.78%, which has a wide range of application prospects.