This paper applies the method of observing, abstracting, problem-solving that the mankind uses in different levels of granularity in real world to the computer network routing. The authors discuss the improved OSPF routing algorithm using the granular computing method of quotient space. The paper describes the thought of granular layering and topological routing, defines the hierarchical dynamic routing (NCR) structure of cluster, domain, group, and establishes the model and algorithm of granular OSPF routing based on the quotient granular space. At last it puts forward the improved test results of algorithm simulation of hierarchical routing algorithm based on quotient space theory.