Under the background of the rapid construction and development of the Chinese electricity spot market, the flexibility and economic requirements of spot market for power grid make the traditional power grid planning methods not applicable.The challenges of power grid planning under spot market are analyzed. The economic benefits are represented by social welfare, including generation surplus, power user surplus and blocking surplus, and the benefit/cost index is constructed to represent the economic benefits of power grid planning. By calculating the shadow price of the line which can reflect the extent of the line congestion,sorting it to determine the extent of the blocking, determining the location of the planning and upgrading equipment and upgrading priority of the device, the power grid planning method which is suit able for the starting and mature stage of the spot market and considering the economic benefits of the spot market is put forward. Finally, an example is constructed to show the flow of economic verification method of planning scheme.