Egenhofer and Franzosa's 4-set model for topological relations is the most common one in qualitative spatial reasoning．However，it is hard to derive the complete set.concept neighborhood，and composition table for topological relations based on 4-set model．In this paper，based on fundamental topology theories，the concept of(n，n)complete set is proposed and the closed ball model is constructed．It is easy to get(n，n)com Dlete set and concept neighborhood，and possible to derive composition table for topological relations based on closed ball model．It is shown that closed ball model is a valid model for topological relations and iS simpler than 4-set model．