Abstract: It's very important to master the law of population. This paper predicts the population's dynamic variety of Changchun City by system dynamic mode. It draws a conclusion that immigrant population made a great contribution to increasing of Changchun City's population.Furthermore,the immigrant rate,the increasing rate of employment post,the house increasing rate and bearing index of women are sensitive variables which affect the population greatly.By controlling these variables,the methods which the emphases include controlling immigrant rate's transforming economic development mode's, improving work efficiency and adjusting the structure of labour are put forward. The progress trend of the population system under these countermeasures was also simulated.

Key words: Northern China semi-arid region, Rainwater harvesting for supplemental irrigation, Water-saving agriculture, Developing model