Compared with current distributed networks, Software defined networking is an innovative technology to manage networks by a centralized controller with global visibility. OpenFlow is one kind of SDN protocols. It provides flow-level controllability of network traffic to simplify the management of the administrators of data center. Flow control rules used by OpenFlow in switch flow table are called flow entries. Modern commodity switches use TCAM to implement flow table because of its high matching speed. However, the general TCAM size of switch only accommodates up to thousands of flow entries due to its high cost-to-density ratio and high power consumption. It indicates that the maximal number of flow that can be controlled is restricted to the TCAM size of switch. That leads to several scalability issues, especially in a data center. In this paper, we propose a topology based flow entry management (TFEM) technique, which is a scalable and memory-efficient solution by exploiting the hierarchical topology characteristic to aggregate the uses of flow entries for most of the small flows in a data center. With the proposed downlink and uplink separated flow tables structure, our results show that TFEM can reduce the average number of flow entries by 50%∼78% for fat-tree topology against the traditional SDN without any switch hardware modification.