In the automatic voltage control (AVC) system implementation process, optimizing reactive power is the core and foundation, and the reactive power optimization in automatic voltage control (AVC) has a higher requirement on computation speed and robustness. AVC system is a distributed control system, the centralized decision hierarchy control, supervisory control and data acquisition (SCADA) is the core of data processing and control systems. Combined with the influence of the harmonic wave in Tangshan power grid, AVC system is applied to research and development from the practice perspective. The result shows that the application of the AVC system not only can decrease power loss and action time of control devices, but also can increase busbar voltage qualified rate and power factor.