The invention provides a single-phase grounding fault line lookup method. The method comprises steps: according to the PT voltage indication value of a bus, happening of grounding fault to a feed-outline of the bus is determined; the zero-sequence capacitive current of each feed-out line cable of the bus which is determined to have grounding fault is tested respectively and recorded; the test value of the recorded zero-sequence capacitive current of each feed-out line cable is compared and analyzed; and when the zero-sequence capacitive current value of the feed-out line cable of the bus which is determined to have grounding fault is larger than the zero-sequence capacitive current value of each of other feed-out line cables and the difference with the sum of the zero-sequence capacitivecurrent values of other feed-out line cables does not exceed a first set maximum difference, the feed-out line of the feed-out line cable with the maximum zero-sequence capacitive current value is determined to be the line with the grounding fault. The method can effectively judge a line with grounding fault, the lookup efficiency and the lookup accuracy of the fault line are improved, grounding fault is further eliminated as soon as possible, power line supply is restored, and the power supply reliability is improved.