Based on the fact that the grid voltage of distribution network with distributed generators connected usually contains low order harmonics caused by adjacent nonlinear loads，a phase-locked loop（PLL）structure is proposed for single phase grid-connected inverters.The proposed method has a coupling feedback structure composed of a main module and multi notch filters，in which the main module aims to estimate fundamental component and multi notch filters aim to get harmonic components.The main module is an amplitude-frequency-phase-locked loop（AFPLL）using gradient descent method.The harmonic modules are simple second order notch filters（NFs）.The complex structure can eliminate steady state errors in dealing with harmonic distorted grid voltage.Finally，the proposed PLL is verified by harmonic distorted grid voltage synchronization experiment，phase mutation experiment，amplitude mutation experiment and frequency mutation experiment.The experimental results show that the proposed PLL not only can eliminate steady state error in harmonic distorted grid voltage，but also has a quick response when grid voltage suddenly changes.