Abstract: In view of the not connected enough between the monthly energy trading and generation dispatching in electricity market, hydropower plant often have the problems of over-generating energy, under-generating energy and seriously spilling water. Therefore, this paper presented a decomposition and checking model for large-scale hydropower plants monthly trading energy. Two objective functions were to minimize progress deviations of that day between the monthly power generation and planned power generation in the flood season and to minimize deviations between the total power generation and planned power generation in the dry season. The solution is that the daily load was predicted by rolling. The remaining load was calculated by deducting the thermal, wind, solar and parts of hydropower generation from the daily load. Then, the monthly trading energy was decomposed to daily with the heuristic information of the completion progress deviation. The constraint conditions of water balance, load balance, electricity balance and section limit were checked. The model was demonstrated using large-scale hydropower plants on Lancang River, Jinsha River, Honghe River and Yiluowadi River. The results show that proposed model can realize the effective correlation between monthly energy trading and generation dispatching. It effectively alleviates the problems of over-generating energy, under-generating energy and seriously spilling water of large-scale hydropower stations and ensure the safety of the power grid