Abstract: Building a new power system is an important way to achieve the goal of "carbon peaking and carbon neutrality", and ensuring the security of the power system is the basis and premise of power transformation and development. In the process of transforming and upgrading the traditional power system to a new power system, the production structure, technological foundation, and control foundation continue to change. The traditional security issue has mainly focused on the stability of the AC power system, and gradually evolved into a "Three in One" security issue composed of power supply security, system security and stability, and unconventional security. It is necessary to re-examine the existing security defense system. This article analyzes the changes in the characteristics of new power system security issues and the adaptability of security defense system. With a problem oriented approach, it systematically considers the construction goals and ideas of the new power system security defense system, and further proposes a research framework for key security defense technologies, providing a reference for the construction of new defense system and related research work.