The invention discloses a power grid operation and maintenance cost prediction method and prediction system. The method comprises the following steps: acquiring basic data related to the power grid operation and maintenance cost, wherein the basic data comprises the electricity consumption of the whole society, the GDP, the power consumption structure, the power grid valid asset net value, power transformation capacity, the line length, and the operation and maintenance cost; inputting the basic data acquired in the above step into a pre-established power grid operation and maintenance cost prediction model to compute, and outputting the expected power grid operation and maintenance cost. The power grid operation and maintenance cost prediction method and prediction system are used for predicting the operation and maintenance cost of the regional power grid, and can provide scientific data support for the power transmission and distribution cost checking, the power grid project feasibility research and post project evaluation and like works.