The invention provides an active rectifier which is applicable to a wireless charging system. The active rectifier is connected with first to fourth switching elements in a bridging mode, and each switching element is connected with a comparator and a reference voltage switching device. According to each of the reference voltage switching devices, the time for each switching element to operate based on its own parasitic capacitance is eliminated, so that the conversion efficiency of the active rectifier can be improved. Therefore, the high-efficiency active rectifier provided can stably work in the wireless charging system with a wide input current range, and can be applied to a system requiring high efficiency.