The invention discloses a power distribution grid fault positioning method with high precision and low cost. According to the fault positioning method, a small amount of traveling wave detection devices with GPS time comparison functions are mounted at two ends of different overhead lines and cable lines of a power distribution grid; when the power distribution grid has faults, the wave speeds of traveling wave line mode component and floor mold component in different lines are calculated by using detection devices of a non-fault line, subsequently the distance of a fault point to one detection device is calculated according to the time difference of the traveling wave line mode component and the floor mold component reaching the detection device, and finally the position of the fault point is confirmed according to the ranging result of a plurality of detection devices. The power distribution grid fault positioning method can achieve accurate fault positioning, shortens the time for troubleshooting, improves the power supply reliability, is small in mounting equipment quantity and good in economy, and has very good practicability.