In traditional regional grid voltage reactive power optimization, only the bus voltage is considered to be within the qualified range, and the medium-low voltage distribution grid is based on the voltage of the upper stage voltage. However, in actual operation, the voltage regulation capability of the medium-low voltage distribution network is often insufficient to ensure its voltage qualification rate, and the upper-level power grid needs to adjust its voltage according to the actual requirements of the lower-level power grid. This paper presents a regional voltage reactive power optimization strategy based on the voltage qualification rate evaluation function. By establishing the voltage pass rate model of the low-voltage distribution network zone and medium-pressure zone in turn, a three-level voltage reactive power optimization strategy for the low-voltage zone, medium-pressure zone and regional power grid is formed. The voltage qualification rate evaluation function is established step by step, making the regional voltage and reactive power optimization strategy well consider the impact on the voltage qualification rate of the lower-level power grid, and solving the problem of coordination and optimization of voltage and reactive power of the upper and lower three-level power grid. The simulation results show that this strategy greatly improves the comprehensive voltage qualification rate of the regional power grid and has high economic benefits.