As the reactive power control range of gateway in the traditional nine-zone automatic voltage control (AVC) strategy cannot adapt to the changes of operation modes,the correlation characteristic between the active loss and the reactive power of gateway in a 110 kV power grid is analyzed,and an optimization-oriented control strategy of the reactive power of gateway and a setting basis of the optimization-oriented network loss increment ΔP are proposed.Then,the reactive optimization interval of a 110 kV power grid gateway is discussed by using the boundary conditioned parameter,and a differential reactive power control range of gateway,which can adapt to dif- ferent operation modes,is obtained.Moreover,the relevant control range is quantitatively assessed by using an e- valuation model.Case analysis shows that the proposed method can improve the economy and safety of power sys- tems and is easy to implement.