The power system is enabled to become more complicated due to large regional power grid interconnection, so there is a big limitation when voltage regulation and control problem is solved by the traditional mathematical methods. In order to increase rate of qualified voltage and minimize investment cost of the new reactive power compensation device, the mathematical model is established in this paper, and it is solved by co-evolution genetic algorithm. The control variable of voltage optimization problem is divided reasonably to reduce computational complexity of the search space and search for optimal solutions cooperatively. The result of example indicated that rate of qualified voltage is improved efficiently by CGA which convergence performance is good, and CGA is helpful to solve large-scale grid voltage regulation and control problem.