The constant parallel RLC loads can't accurately reflect the practical performance of the islanding detection. In order to solve the problem, the comprehensive load model including voltage and frequency dependence is adopted and it accords with the actual operation of the power system. The detailed study of the performance of the Sandia Frequency Shift (SFS) method is carried out under this condition. The theoretical analysis shows that the load active power voltage/frequency dependence and quality factor have a significant impact on the nondetection zone (NDZ), and the effect of reactive dependency is negligible. In this paper, the impact of the comprehensive load’s parameters on the NDZ is analyzed, and the research provides a theoretical basis for the practical application of the islanding detection. The simulation results demonstrate the validity of the theoretical analysis.