In order to solve the problem of single-phase ground fault characteristics of small current grounding system, the fusion criterion based on DS evidence theory is proposed by wavelet theory. Firstly, the wavelet base and wavelet decomposition scale are determined, and the wavelet energy matrix is constructed to determine the fault characteristic frequency band. Further, three fault characteristics, including wavelet energy ratio, wavelet reconstruction coefficient variance and transient power direction, are extracted in this characteristic frequency band, and the sensitivity of them is analyzed. Considering the different detection sensitivity of each fault line selection feature, the line selection fusion criterion based on DS evidence theory is further proposed in order to improve the line selection accuracy. Finally, the on-site recorded waveform is analyzed. The analysis results show that the fusion criterion can organically integrate three line selection features, improve the line selection accuracy, and has better engineering application value. This work is supported by Science and Technology Project of the Headquarter of State Grid Corporation of China (No. GY71-17-032).