The invention discloses a single-phase grounding fault line selection method based on discrete orthogonal S transform and information divergence. The method includes the following steps that: voltagecollecting devices are installed on lines respectively so as to collect the transient voltage signals of each feeder line during a line fault; a data processing module is connected with the voltage collecting devices and converts the transient voltage signals into zero-mode voltage components; the data processing module sends fault starting signals to an upper computer, and a zero-sequence currentcollecting module installed on the lines collects the zero-sequence current signals of each feeder line and sends the zero-sequence current signals to the upper computer, discrete orthogonal S transform is performed on the zero-sequence current signals, so that the information divergence of each feeder line is obtained, a line with the largest information divergence is a single-phase grounding fault line. With the method of the invention adopted, the information divergence is solved through initial-half-wave zero-sequence current parameters, so that the selection of a single-phase grounding fault line in power distribution lines can be realized; the capacity of the discrete orthogonal S transform to divide the frequency bands of the transient signals and the capacity of the information divergence to distinguish the small differences of the signals are comprehensively considered, and therefore, the reliability of line selection is improved.