The invention discloses a power distribution network line fault on-line monitoring and positioning system. The power distribution network line fault on-line monitoring and positioning system comprises a line fault indicator, a wireless acquisition device, a wireless ad hoc network and a monitoring main station, wherein the wireless acquisition device is in wireless communication with the monitoring main station through the wireless ad hoc network, the wireless ad hoc network comprises a central node and multiple sensing nodes. The central node and the multiple sensing nodes are connected in a wireless communication mode, and the multiple sensing nodes are connected in the wireless communication mode. The invention further discloses a communication method adopted by the power distribution network line fault on-line monitoring and positioning system. A networking method of the wireless ad hoc network comprises the following steps of initializing node electrification, starting to perform networking, finding neighbors and measuring field intensity, collecting the field intensity, performing route planning and configuration and performing normal work. By means of the system and the communication method, the power distribution network line fault on-line monitoring and positioning are performed, the networking can be performed quickly, a structure is flexible, data transmission is reliable, received data are complete, wireless communication signal dead zones do not exist, only one-time investment is required, operation expense is not required, and the operation cost is reduced.