The object studied is singlephase feedback type electronic load, the principle of Sandia frequency shift islanding detection(SFS) is analyzed in detail, nondetection zones are evaluated, and optimizing parameters of SFS algorithm. Meanwhile, SFS and Sandia voltage shift method (SVS) are combined to form a complex of islanding detection method with passive methods of over/under frequency and over/under voltage. Finally, the model of simulation are conducted in with the help of MATLAB/Simulink. The simulation results indicate that the system can be conducted without nondetection zones under special loads. The combination with SFS and SVS will significantly improve the detection efficiency,and it can carry islanding protection quickly and efficiently, and power quality is higher, the feasibility and the superiority of the scheme are verified.