Abstract: Cellular Automata has been used in simulation urban extension. But we cannot ensure the rationality of simulated results since it had adopted the rules of static, single and unrestricted variable. We established a new model named as GeoObjectCA-Urban which was based on urban geographical objects. We analyzed three factors of this model such as landuse, transport and control condition, and gave the expression methods and structure of the cellar. Especially, we emphasized on how to simplify the parameters and the transferred rules of cellar state change during building this model. And we developed corresponding tools to accomplish this task. At last, we illustrated this model by Yiwu city. The result proved that this model was flexible and exercisable.