The early warning and security countermeasure（EWSC） system is a new development of the control center system. The functions of this system are being evolved continuously and the energy management system（EMS） is also necessarily preserved in the implementation of the EWSC system. In this paper， an agent-based software development paradigm is proposed and deployed in the EWSC system software framework. This system has an open and loosely coupled plug-in architecture， of which the kernel is called the core framework， while the other components are independent modules that can be developed individually and are easily embedded in the system. Furthermore， the EMS can be conveniently wrapped and integrated into the EWSC system. The application of the EWSC system in a provincial power system shows that the design of the system is rational and practical.