With the development of the economy and the increase of the population in the cities, traffic jam has become a serious problem. It brings a threat to the harmonious development of urban economy and society. How to solve or alleviate the "bottleneck" of the traffic jam in the cities has become an important discussion issue confronted by all the levels of the governments in China. Many counter-measures have been taken as possible as we could.
Utilizing the nonlinear theory, this paper attempts to make a research on the dynamic relationship between the acreage change of the roads and the population in the cities, and forecasts their developing trends. Through setting up the nonlinear dynamic model of the roads and the population in the cities, the paper also analyzes their essential relationship. The results show that the stable population in the cities is positive to the stable road acreage occupied by the flow passengers; the increase of road acreage is constrained by the maximum road acreage; the amount of road has a proportion to the maximum amount of population and inverses to the road flow capacity. The utility rate of the resources will be improved and the communication system will be managed well so as to increase the flow of goods and passengers. From the research, we can see that it is vital for us to balance the population and the economic development.