For accurately evaluating the practical performance of the islanding detection, a circuit with rectifier load for the islanding test is proposed based on the conventional test circuit. According to the law of power flow at the point of common coupling (PCC), the expression of power mismatch is obtained. Under different power mismatch, respectively based on the proposed circuit and the conventional test circuit, the detection methods including over/under voltage, over/under frequency and voltage harmonics are analyzed through simulation and comparison. The simulation results show that the rectifier load has made non-detection zone (NDZ) deviate and the degree of deviation is related to the resistor and the filter capacitor of the rectifier load. The results also show that the proposed circuit is valid and practical. It can accurately reflect the actual response characteristics of voltage harmonics when islanding occurs and the voltage harmonics is related to the resistor of the rectifier load.