A method and a device for quickly locating faults of an overhead line on the basis of time synchronization belong to the technical field of intelligent grid distribution automation. The method for quickly locating the faults of the overhead line on the basis of time synchronization comprises a distribution overhead line and a master station and is characterized in that a plurality of distribution data collection units arranged on the distribution overhead line collect voltage signals of the distribution overhead line and current signals of each branch through the time synchronization technology, collected data with time labels are transmitted back to the master station to achieve calculation and judgment on the branch where the faults happen, and position information of a fault interval and the fault state of a line are displayed. The device consists of the distribution data collection units, a time reference unit, a communication system and a master station system. By utilizing the method, the device can automatically judge a fault section of a power supply line, provide the position information of the fault interval, especially improve accuracy of single-phase grounding fault judgement, replace with small current grounding routing system of a transformer station, reduce a power failure range, shorten line reparation time, and improve power supply reliability of a power supply system.