Abstract: The article uses the possibility-satisfaction ability method of system engineering to build the forecasting model of the reasonable population scope in our city.It incorporates lots of factors in five aspects that are the level of economics,social living,level of resources,environments and strength requires,and finds the reasonable population scope and the conditions that the scope relies on at an objective time.The article proves its effectiveness by means of demonstration.

Key words: reasonable population scope, possibility-satisfaction ability, systematic forecasting