The invention discloses a method and system for real-time automatic distribution of gate opening of a cascade hydropower station. The system includes a collection terminal, database server, application server, process library, policy library, information publishing cat, and remote control system, a collection element, transmission element, simulation element, and constraint element are arranged onthe application server and are connected with the database server, process library and information publishing cat. The invention can adjust the gate in advance, at the same time, the opening degree of each gate of the preset dispatching strategy is given by using the subsection step-size mutation algorithm, In addition to real-time monitoring of reservoir water level, effectively shorten the timeof making gate opening, A good balance has been struck between flood control and flood resource utilization, In order to reduce the working intensity of the operators and accurately control the waterlevel of the reservoir, the calculation process is simple and quick, and the follow-up effect of cascade flood control storage capacity under different flood discharge is taken into account, so as tomeet the needs of the actual operation of the power station for the calculation result accuracy, safety, real-time performance and economy.