The happening of the island will bring people not only a serious security threat, but also a series of problems, like leading to a damage of system equipment. Therefore, photovoltaic grid power system must be equipped with the islanding detection function to ensure the safety of the power grid. The traditional AFD’ detecting effects is different under different loads, and it’s good for the impedance load. Although the improved AFD based on feedback adjustment or periodic disturbance proposed by former researchers can reduce the THD, the detecting speed slowed down at the same time. In view of this, this paper proposes a new active island detection method based on a novel perturbation way, it has the lower THD, the smaller blind area and the more faster detecting speed compared with the traditional AFD, so it has a high practical value. Matlab/Simulink simulation and the experiment results show that the new method is better than the traditional AFD.