The invention discloses a judgment method for a circuit grounding fault in a low current grounding system. The method comprises the steps of S1, measuring a zero sequence current value of each circuitin the low current grounding system; S2, randomly switching off a circuit, and measuring the zero sequence current values of the other circuits; and S3, carrying out comparison on the zero sequence current value of each circuit measured in the S1 and the S2, wherein in addition to the cut circuit, the circuit with the highest zero sequence current value change quantity is a fault circuit. According to the method, theoretical analysis is carried out for a zero sequence network in a single phase grounding process, and the fault circuit can be determined through utilization of an equation relationship of zero sequence parameters and a change relationship of the zero sequence parameters after the circuit is switched off. The method provided by the invention is rapid and reliable. The fault circuit can be simply, effectively and rapidly detected. The basis for overhauling is provided.