In order to solve the problem that single-phase grounding fault detection (especially high-resistance grounding fault) in traditional distribution network is affected by weak fault characteristics and difficult to detect, this paper proposes a new detection method for single-phase grounding fault detection in eutral point ungrounded distribution network based on two-terminal measurement of power factor angle from the perspective that the power of distribution network system will change significantly before and after the fault. The two voltage transformers connected with the neutral point inject controllable current signals into the neutral point and measure the return voltage signals, so as to accurately measure the active and reactive power of the distribution network at the current operating state, and then obtain the power factor angle of the system. Combined with the power factor angle of the distribution network under normal operation, the ratio coefficient of power factor angle before and after the system failure is measured in real time. Based on the comparison between the ratio coefficient and the ratio threshold coefficient, the sensitive detection of high resistance grounding fault is realized. The smart application of dual voltage transformer eliminates the measurement error caused by internal resistance and detuning resistance of the transformer in principle and greatly improves the effective detection range of high resistance grounding fault in distribution network. The proposed method is verified by setting up a 10 kV neutral point ungrounded distribution network in the simulation environment of PSCAD/EMTDC. Different types of high resistance grounding faults are simulated to verify the proposed method. The simulation results show that the proposed method can detect high resistance grounding faults reliably, and the detection range is up to 20 kΩ.