In the process of the rapid urbanization, there emerge more and more uncertainties for development of the city. It has been diffi cult for the method of forecasting population which takes the natural population growth rate and mechanical growth rate as the basic variable to adapt to the objective trend. Against to super-normal population growth in the city, this paper proposes the method of forecasting population and forecasts the population size of Changshou downtown area in the perspective of essential reasons of permanent resident population.