The invention relates to a method and a system for evaluating utilization efficiency of a planning power grid scheme. The method comprises the following steps of 1) considering a power grid load growth rate and new production power equipment in the planning year based on pre-collected basic data of a current power grid, and forming a topological structure, a load vector and a power plant output vector of a planning year power grid according to a production sequence of the planning power grid schemes; 2) carrying out power grid production operation simulation through load flow calculation in order to obtain production operation simulation result data of the power grid under each planning power grid scheme; 3) calculating to obtain a power grid utilization efficiency evaluation index value of each planning power grid scheme according to the obtained production operation simulation data of each planning power grid scheme and a pre-established power grid utilization efficiency evaluation index; and 4) calculating an efficiency benefit improvement score of each planning power grid scheme, and evaluating different planning power grid schemes according to the score conditions in order toobtain a planning power grid scheme with the optimal efficiency benefit. The method and the system can be widely applied to planning power grid scheme evaluation.