The invention discloses a method for optimizing a power transmission network structure of a power system with wind and photovoltaic power sources. According to the method provided by the invention, anoperating state of a grid power transmission element is brought into an economic dispatch model of a power system; and the model is calculated by combination of a particle swarm optimization algorithm with a non-linear planning interior point method. Decision making is carried out on active outputs and grid power transmission element states of conventional and renewable energy source generator sets in the power grid in advance, so that the economy of grid operation is improved on the premise that the grid voltage support is ensured, the conflict of absorption of renewable energy sources is relieved and thus the renewable energy source is absorbed in a large range for power generation. Therefore, an effective method is provided for economic dispatching of a power system under the background of renewable energy source large-scale grid connection.