In this paper, a new Distribution Management System (DMS) framework based on security region is proposed. First, the concept of Distribution System Security Region (DSSR) is introduced. DSSR is capable to describe the N ? 1 security boundary of the whole distribution network, including the secure output range of DGs. This new theoretic tool provides a chance for the implementation of real-time security analysis and active controls in DMS. Second, this paper proposes and describes five security states for distribution system. Third, an upgraded DMS enhanced with DSSR is proposed, which consists of advanced security functions such as preventive and predictive control of the trajectory of operating points. Finally, a practical case is presented to simulate the proposed DSSR-enhanced DMS, in which both the security region of network and the output range of DGs are calculated. Typical security functions are also demonstrated. In conclusion, the new DMS framework aims to help operate the system closed to its security boundary in order to improve the efficiency significantly within same security standard. This work is beneficial for future low carbon distribution systems with high penetration rate of DGs.