The present invention is to provide a method for selecting the optimal central controller in a power line network, which is applicable to the power line network including at least one terminal device, at least one network device and a plurality of controllers. The controllers are respectively installed with a central controller evaluation and selection software and connected to the terminal device and/or network device, and can communicate with one other through power line. The method is performed by a central controller, that is determined by negotiation between the controllers, via the software and includes the steps of detecting and calculating the connected states of the controllers in the power line network; selecting the optimal controller according to the connected states, assigning the optimal controller as new central controller, and notifying the new central controller to the other controllers, so as to optimize the performance of the power line network.