This study solves the problem of distributed photovoltaic active island detection in network access point.The research proposes a research based on impedance measurement. The research introducts the signal generator in network access point to produce high frequency signal which is better than the present passive island detection algorithm. This measure can judge system impedance changes actively to detect the state of islanding of micro grid and photovaltaic. And it furtherly eliminate the detection blind area. At last, we simulated the active island detection algorithm,and the results show that the detection method can effectively avoid detection blind area and ensure the safety of grid, and it makes not much impact to original micro network.