The invention discloses a power grid planning scheme evaluation and optimization method and system based on full-cost electricity price, and the method comprises the steps: obtaining the basic data ofa power grid, and calculating the node marginal power generation cost, the node unit load power construction cost, and the node unit load power operation and maintenance cost according to the basic data of the power grid; linearly adding the node marginal power generation cost, the node unit load power construction cost and the node unit load power operation and maintenance cost to generate a power grid full-cost electricity price; establishing a power grid planning evaluation index system according to the full-cost electricity price of the power grid; and assessing the plurality of power grid line planning schemes according to the power grid planning assessment index system, and optimally selecting an optimal power grid planning scheme. The method can comprehensively evaluate the safetyand economy of a power grid planning scheme, is beneficial to improving the lean level of power grid planning, and can provide a quantitative analysis method and an auxiliary decision-making tool forinvestment planning of a power grid company under the background of new power transformation.