The invention discloses a power distribution network grounding line selection method based on distributed power distribution terminal devices. According to the method, the power distribution terminal devices complete the grounding line selection work through improving the existing method and mutual data interaction of the distributed power distribution terminal devices so that reliability and rapidity of line selection under the situation of single-phase grounding fault in a small current grounding system can be enhanced. According to the method, manual participation can be avoided or reduced, a monitoring system host or an independent line selection device is not required, signal injection source equipment is not additionally installed, and different algorithms are matched with different modes of small current grounding systems for analysis so as to enhance the correct rate of line selection. Meanwhile, data analysis is dispersed to all the power distribution terminal devices to be synchronously performed so that the problems of waste of resources and low reliability caused by the fact that analytical calculation is concentrated on one set of equipment can be avoided.