There are problems of large blind spots in passive detection and dilution effects in active detection. Thus this paper proposes a multi-distributed generation (DG) islanding detection method based on active/passive combination. First, this method uses an active power filter (APF) to achieve reactive power disturbance. This controls the reactive power output frequency of 2 Hz by perturbing the q-axis parameters of the APF, in order to perturb the periodic fluctuations of islanding frequency. Then, wavelet decomposition and wavelet reconstruction algorithms are used to extract low-frequency components from frequency signals. Finally, the fast Fourier transform (FFT) algorithm is used to calculate the amplitude of the 2 Hz low-frequency component and determine whether it is out of limit, to achieve multi-DG island detection. The modeling and simulation results using Matlab/Simulink show that this method can effectively avoid dilution effects and achieve multi-DG island detection.