A method and a system for controlling LED with power line carrier are disclosed. The system contains a host controller, an electric power conductor, and at least a luminous device, and the luminous device further containing an environmental data collection module. The method comprises the steps of providing a power line carrier module to both the host controller and the luminous devices; the luminous devices detecting a set of environmental data by the environmental data collection module; the luminous devices transmitting the set of environmental data to the host controller; the host controller recording and analyzing the set of environmental data; and the host controller sending a control signal to the luminous devices according to the analysis. Therein the control signal and the set of environmental data are transmitted by the power line carrier module through the electric power conductor.