With the expansion of IP networks, a diversity of network management systems have been developed in order to support network operations. Based on the common functionalities of these network management systems, a platform for network management systems was developed by KT, on which future network management systems could be developed on the platform. However, in the process of the development, it was discovered that the reusability of platform modules was stagnating at around 30%. In order to further increase reusability in developing network management systems, this paper proposes a proactive reuse method to build a flexible network management topology architecture. The goal of the method is to overcome the limitation of the reusability approach that utilizes a platform for network management systems developed based on only common functionalities.