The resolver is a commonly used motor rotor position detection device, and its detection accuracy directly affects the performance of the entire control system. In order to obtain highprecision rotor position information, a software resolvertodigital converter (RDC) combined with error compensation is analyzed. Firstly, the position angle solution method based on the threephase synchronous reference frame phaselocked loop (SRFPLL) is adopted to filter out the highfrequency jitter component in the resolver output signal. Then, aiming at the influence of the zero error, quadrature error and amplitude error in the resolver output signal, the ellipse hypothesis algorithm is used to eliminate it, and the harmonic separation method is proposed to realize the compensation of the harmonic error in the signal. Finally, a simulation model and test platform are built for analysis and verification. Simulation and test results verify the effectiveness of the proposed method.