The invention discloses a power distribution network topology automatic identification method, device and system based on power line communication. The method comprises the steps of ste 1, collectingID information and state information of each switch node in a power distribution network; step 2, calculating the distance d between every two switch nodes; and step 3, performing power distribution network topology based on distance information identification, ID information and state information between the switch nodes. According to the invention, by adopting a switch node distance measurementalgorithm based on relative clock calculation, the actual distance between the two slave devices is solved by adopting a relative clock calculation principle according to the time scale characteristics and the power line communication rate of the two slave devices in the information interaction process. A collinear judgment principle is combined with an adjacency relation judgment method, a powerdistribution network topology model containing distance identifiers is established, and automatic topology recognition is achieved. The topology information identified by the scheme is more accurate,and the investment cost and the operation and maintenance workload are lower, so that the method has a very high application value.