As the interconnectivity of the power grid increases, various risks associated with the overall defense system, including network boundary protection, entity security protection, and core application protection, pose a threat to network security. Existing solutions mainly include deploying boundary protection devices, identifying entity vulnerabilities, and detecting abnormal application activities, but these solutions lack sufficient differentiated security protection measures and blocking capabilities. Therefore, the paper proposes a power node division method, which involves dividing nodes into levels based on their importance and implementing differentiated defense measures accordingly. This results in the construction of a three-level vertical defense system based on differential defense proposals, namely "boundary defense, self protection, application monitoring". The solution implements fine-grained differential defense measures based on node grading, formulates general defense strategies for low-level nodes, and executes customized defense measures for high-level nodes, making the allocation of defense resources more reasonable, ensuring the security of power nodes, and improving the security defense capabilities of the power supervision and control system.