The invention discloses a system and method for security defense of an embedded terminal and belongs to the technical field of smart power network security. The system comprises a security threat detection unit which comprises a distributed data collection module and a security threat detection module; a security threat isolation unit which comprises an isolation policy making module, a terminal isolation module and a network isolation module; and a self-healing unit which receives network isolation information and terminal isolation information, and comprises a self-healing policy making module, an attack source tracing and elimination module, a terminal self-healing module and a network self-healing module. According to the system and the method, when a power network embedded terminal suffers from a security threat, the terminal is enabled to recover to a normal operation state timely and effectively, and further, secure and reliable operation of a power industrial control system areensured.