The invention discloses a power grid operation mode generating method based on a monthly power transmission and distribution equipment maintenance plan, and belongs to the technical field of an electric power system and automation thereof. The power grid operation mode generating method is characterized by comprising the steps that original data of the operating mode is acquired from a power grid regulation and control center, a peak load operating mode and a valley load operating mode of each day having the power transmission and distribution equipment maintenance plan are monthly generated according to the monthly power transmission and distribution equipment maintenance plan and load rate distribution monthly electric quantity prediction data of different time periods of the corresponding historical period, influences of system network losses, spinning reserve requirements and planned outage units are considered in the process of generating the two modes, and power grid operating mode data under the power transmission and distribution equipment maintenance plan according to a date-load mode is finally acquired. The maintenance plan operating mode generated according to the method disclosed by the invention conforms to production requirements and habits of the electric power system, thereby being capable of providing a data basis for power grid operating risk evaluation and maintenance plan readjustment under the power transmission and distribution equipment maintenance equipment plan of the electric power system.