The invention discloses a mid and low-voltage distribution network fault positioning method. The method comprises steps: 1, through a power consumption information acquisition system, a distribution line online monitoring system, a residual current operated protective device monitoring system, a dispatching automatic system, a distribution network automatic system and a production management system, power consumption information of the mid and low-voltage distribution network is acquired, the power consumption information of the mid and low-voltage distribution network is corrected through a power flow distribution algorithm, and the topological relationship of the mid and low-voltage distribution network is perfected; and 2, according to power loss information in the power consumption information of the mid and low-voltage distribution network, based on the topological relationship of the mid and low-voltage distribution network, fault study and judgment are carried out through a corresponding fault study and judgment algorithm, a fault device is determined, devices and users influenced by power failure are analyzed, and a geographic area influenced by power failure is generated when a power grid device and the geographic position information of power grid users are combined. The method of the invention has the advantages of high fault positioning precision and high power failure range judgment precision.