Abstract: The new type power system realizes the extensive interconnection of new energy sources and diversified loads, as well as the dynamic interaction of cyber flow and energy flow, but it also faces more and more serious security threats. The attackers can launch cyber attacks to cause a series of spatiotemporal coordinated power faults at multiple power nodes, forming cross-domain cascading failures (CDCF), and undermining the stable running of new type power system. In this context, the evolution and active defense mechanism of CDCF are studied. Firstly, the coupling security risks of new type power system are analyzed based on the system architecture and running characteristics. After that, an event-driven analysis is carried out on the whole attack process of CDCF caused by the attackers, and a CDCF mathematical model is established. Finally, the active defense process of CDCF is analyzed from the defenders’ perspective. A CDCF active defense mode is proposed considering the characteristics of new type power system, and a decision-making model for the optimal active defense scheme is established to provide the technical solution for CDCA active defense.