Main transformer capacity is decided by the computational load when transformer substation is planning. The computational load is a static content forecasted by the load when transformer efficiency reaches the highest. But the actual load is a dynamic content which is changed with time. When transformer substation is in operation, it needs several years when the actual load reaches the computational load, during these years, the transformer is in light-load condition, which will increase power loss, causing economic losses, and aggravating environmental pollution. This paper is proceed from the contradictory fact between transformer capacity and load development, and proposes a transformer capacity ladder-type configuration plan based on dynamic load characteristics. The plan is to deploy transformer capacity gradually based on the dynamic load characteristics. Finally the paper compares technology and economic benefit between two plans, and verifies the superiority. Its conclusion is used to guide the initial planning of urban substations.