Abstract: Aiming at the reduced accuracy of the synchronous reference frame phase-locked loop (SRF-PLL) caused by the grid voltage harmonic distortion or three-phase voltage imbalance and the limited dynamic performance of the traditional moving-average-filter-based phase-locked loop (MAF-PLL), this paper proposes a novel three-phase phase-locked loop algorithm based on the fractional-order PID controller and MAF-PLL (FOPID-MAF-PLL). Compared with MAF-PLL, the proposed FOPID-MAF-PLL compensates the phase lag of MAF by incorporating a fractional-order differential term into the PLL, therefore, the dynamic performance of the PLL can be improved effectively. Furthermore, the design process and parameter tuning of FOPID-MAF-PLL are also given in this paper. To enhance the frequency adaptability of the proposed PLL, the frequency variation extracted by the intermediate link of the PLL is used to modify the control parameters of FOPID-MAF-PLL online, thus, the frequency-locked and phase-locked capabilities can be guaranteed when the grid frequency fluctuates. Finally, the efficiency and superiority of the proposed FOPID-MAF-PLL method are verified by simulation and experiments.