Accurate identification of distribution network fault type can provide directive guidance for the operation and maintenance personals of transmission lines. In this paper, a new fault rootcause identification method of distribution network based on the time and frequency characteristic analysis of fault waveforms is proposed. Through model building and theoretical analysis of different types of fault waveforms, the characteristic parameters are proposed, which can characterize different kinds of fault waveforms from time domain, frequency domain and arc model. The formulas for calculating characteristic parameters from fault waveform data are proposed. Multiple characteristic parameters are fused, and based on which the classifier is built; the fault types of the distribution network caused by different rootcauses are identified automatically through detecting and analyzing the characteristic parameters of the input waveform data. Finally, the proposed classification method was tested and verified using 136 groups of different field fault waveform data provided by EPRI; the test results show that the successful identification ratio reaches to 90%, which verifies the feasibility of using fault waveform time and frequency characteristics to realize the fault type identification of distribution networks.