An improved electro-search algorithm(IESA) is proposed to solve the problem of long computing time in the process of joint optimal operation of reservoirs. Based on the electro-search algorithm, the proposed algorithm adopts a new parameter adaptive method to accelerate the migration speed to the global optimal solution in the early stage of operation and has strong local search ability in the later stage of operation. At the same time, according to the characteristics of strong constraints of joint optimal operation of cascade reservoirs, two search strategies of searching in feasible region are proposed to make the electrons generated around the core and the migrated nuclei satisfy the feasible region constraints, avoiding the invalid optimization caused by random optimization exceeding the feasible region, and improving the search efficiency. The improved electro-search algorithm is used to solve the optimal operation problem of joint power generation of two reservoirs in Lixianjiang River Basin. The results show that the calculation results of this method are similar to those of the dynamic programming method and are superior to the genetic algorithm, especially in the speed of calculation, which is worth popularizing.