Abstract: As one of the five big systems of the State Grid Corporation of China, the“big” planning system is the premise and guarantee of other four big systems. The reactive voltage planning, as a very important part of the power grid plan, is the foundation for ensuring the economic, reliable and stable operations of regional power grids. By taking the Twelfth Five-Year reactive voltage planning of the Shandong Grid as an example with consideration of importing electric power to Shandong Grid, a calculation was made of the Shandong main grid in terms of reactive power optimization, the stability margin and the ability to resist the interferences on the basis of reactive compensation equipment configuration; the voltage safety level of the main grid was evaluated; and the optimal capacity of reactive compensation equipments was determined to ensure the safe and economic operation of the main grid. This study provides a theoretical and technical support for the building of the “big planning” system of the Shandong Grid.