Aiming at the problem of voltage distortion and frequency fluctuation caused by harmonic interference of the power grid, which affects the stable operation of the power grid, a frequency adaptive phase lock method is proposed. Based on the harmonic extraction circuit, a new second-order generalized integrator (NSOGI) phase-locked loop with the function of filtering out grid harmonics is designed. Using a frequency-locked loop (FLL) combined with a second-order generalized integrator (SOGI). FLL tracks the frequency of the input signal, and has a great deal of distortion and harmonics in the grid voltage. Good suppression, high frequency locking accuracy. The harmonic extraction circuit extracts and utilizes the harmonic current to avoid energy waste caused by direct filtering of harmonics. Compare the frequency deviation in the circuit before and after harmonic extraction with DSOGI-FLL, verify the harmonic extraction effect and phase-locking accuracy of the circuit, and verify the feasibility and correctness of this method through theoretical analysis and simulation.