The invention discloses an automatic regional power grid voltage reactive power control method based on regional strategy optimization. The method includes the following steps of automatic region division, state preprocessing, generation of a strategy set, strategy evaluation, strategy optimization and obtaining of the optimal strategy through calculation of an evaluation function, and thus reactive power control is carried out on regional power grid voltage. According to the method, voltage reactive power optimal control of the whole power grid is decomposed into independent regions to be respectively optimized, after the regions are formed, calculation and strategy optimization are carried out on the various regions respectively, dependency on measurement accuracy of the whole power grid and the state estimation yield of the whole power grid can be reduced, and whole-grid data transmission interfaces cannot be influenced due to poor measurement quality of a part of regions and inaccurate parameters; the number of calculation models is reduced, calculation scales are reduced, and the calculating speed is increased.