The invention relates to the technical field of power transmission and transformation, and discloses a method for positioning a regional DC ground potential fluctuation source. The method comprises the steps of building a substation grounding neutral point direct current monitoring network, acquiring the size and direction of direct current at a grounding neural point, developing direct current distribution calculation software by taking substation direct current monitoring data under a direct current transmission ground-return operation mode in the monitoring network as a basis, deducing direct current distribution at the substation grounding neural point through the direct current distribution calculation software, and comparing the direct current distribution with the size and direction, which are acquired by the monitoring network, of the direct current at the grounding neural point to obtain the position and current size of the fluctuation source. According to the method for positioning the regional DC ground potential fluctuation source, the ground potential fluctuation source is accurately positioned by using the existing regional AC power grid substation system, detection sites are not required to be additionally detected, and the detection cost is greatly reduced.