Abstract: In this paper, it is pointed out that the existing reactive power optimization algorithms cannot solve the allocation problem of reactive power under the coordination of provincial and regional power grid, so the extreme optimal power flow (EOPF) is presented based on the voltage contribution degree and reactive power contribution degree. To meet the requirement of voltage level and the power factor between provincial and regional power grid, the relax optimization can be achieved by selecting capacitors that can effectively improve system voltage level and power factor, and such indexes as the voltage contribution degree and reactive power degree are proposed to realize relative quantification. Suitable capacitors are chosen in EOPF, which can expand the searching region of the optimization problem to find out the optimal solution under different load modes, and relative suggestions on optimization solution mode are provided for departments of system planning and operation. In the end, case study on IEEE 30-buses system and a regional power grid in Sichuan Province is used to verify the flexibility and effectiveness of the proposed EOPF method.