There is a problem of power system frequency stability caused by random fluctuating power and load frequency control (LFC) system parameter changes when wind power is connected to the grid. Thus an optimal PID controller design method based on an intelligent optimization algorithm and improved objective function for an interconnected power grid LFC system is proposed. First, the LFC closed-loop model of an interconnected power system with wind power generation based on PID control is analyzed. Secondly, in the objective function of the performance index of the integral of time multiplied absolute error (ITAE), the output signal deviation of the regional controller is considered, and the optimization objective function is improved. The optimal PID controller parameters are obtained with excellent performance by using the multi-verse optimizer (MVO) algorithm which is calculated first and verified later. Finally, taking the interconnected power LFC system of 4 generators in two regions as an example, the PID controller based on the MVO algorithm, which is obtained by improving the objective function, is verified by simulation. The simulation results show that the PID controller combined with improved objective function has relatively better robustness to step load, random load and wind power deviation disturbances and system parameter change than the PID controller based on the MVO algorithm. It also has a relatively good non-vulnerability index for controller parameters.