On the basis of traditional active frequency drift（AFD） method， an improved islanding detection method is presented adopting the pulse current amplitude disturbance. The method to inject the current amplitude disturbance is introduced， especially the method to choose disturbance time. The islanding detection is simulated in combination with over-voltage protection /under-voltage protection（OVP/UVP） and over-frequency protection /under-frequency protection（OFP/UFP）. The results show that the combined method overcomes the problems associated with AFD or the current disturbing method. Islanding occurrence can be detected effectively with the presented method， and the photovoltaic system can be disconnected from the system before high-speed auto-reclosing， with limited harmonics and reduced non-detection zone.