From the perspective of promoting large-range accommodation of clean energy, under the national unified power market, a risk management and control model of accommodation and water discharge of transferring hydropower is developed in this paper. The model takes a dynamic stability limit of cross-provincial transmission channel as an opportunity constraint. First, a mathematical expression about the cross-provincial transmission dynamic stability limit is constructed, thus it is realized that the management of stability limits changes from static state to dynamic state. At the same time, the concept of semi absolute deviation is used to establish the risk assessment index of water discharge, thus it is realized that deterministic assessment extends to uncertainty assessment. Then, based on the framework of stochastic programming and the proposed concept of risk management of water discharge, and the risk management and control model of accommodation and water discharge of provincial power grid is established in monthly market, so as to control the risk of water discharge effectively. After using some techniques to deal with the dynamic stability limit of the cross-provincial transmission channel, a multi objective genetic algorithm with embedded Monte-Carlo simulation technology is proposed to solve the model. Finally, taking Tibet power grid as an example, the validity of the above work is verified, and the universality of the research is discussed. This work is supported by National Natural Science Foundation of China (No. 51677012), Scientific and Technological Research Project of Chongqing Municipal Education Commission (No. KJ1704101), and Management Consulting Project of State Grid Corporation of China (No. SGSW0000DKWT1900116).