In view of the flaw of a long detection time in traditional islanding detection algorithm, an improved frequency positive feedback islanding detection method has thus been proposed. The islanding detection time can be shortened by the addition of the positive feedback gain coefficienta A and B to the inverter output angle frequency, followed by a tentative investigation on the feedback strength and detection effects of inverter output voltage angle frequency corresponding to different values of A and B. Meanwhile, an analysis has been made of the critical condition for a successful detection of the islanding phenomenon, thus obtaining A and B values of effective detection time. The simulation results are consistent with the theoretical analysis results, which verify the effectiveness of the proposed method.