Lots of city building projects will consequentially affect the usual traffic, now, with the development of economic in our country, the city traffic will endure more and more pressure, so it is important and necessary to evaluate the traffic impact during the stage of program. Through the analysis about the traffic impact in our country, this article takes use of the "district-road network" theory to evaluate traffic, and at last come into being a traffic impact evaluation system based on software, finishes the basic function of traffic impact evaluation.