The invention relates to an optimal matching loop power based method for identifying topological structures of a power distribution network and belongs to the technical field of electric system dispatching automation and electric power network simulation. Load data collected by an electrical power measurement system serve as load measurements; power measurements in the power distribution network are used for calculating the optimal matching loop power of all independent loops of the power distribution network; then a plurality of possible topological structures of the power distribution network can be obtained according to the optimal matching loop power; state estimation is conducted on possible topological structures respectively; and finally, state estimation results and the best matching topological structure of measurements serve as the correct topological structure of the power distribution network. According to the method, branch power measurements in the power distribution network and the load data in the measurement system of the power distribution network are fully used, and the method is simple to implement, fast in calculation speed and accurate in result.