The islanding-detection is important for the DG system. But the traditional islanding-detection cannot ensure the good detecting performance and the electric power quality at the same time. In order to solve this problem, a new islanding-detection method is proposed. This method combines fuzzy control with active frequency drifting with positive feedback (AFDPF), which can choose the coefficients of AFDPF based on fuzzy control. Compared with AFDPF, this method can detect the islanding faster with less impact on power quality when the DG system is connected to the grid, and eliminate the non-detecting zone. When the system is disturbed, the new method does not affect the frequency of system and would not judge it as islanding.