Abstract: In order to raise the information security level of power systems under malicious cyber-attacks, the method based on the nonlinear causal analysis theory is proposed to analyze the vulnerability of grid nodes. Nonlinear causal relationships among nodes of power system were mined through causal qualitative analysis. New vulnerability evaluation indices were defined, and the vulnerability of nodes was ranked through causal quantitative analysis. Under different attack strategies, the simulation experiments of power systems show that compared with traditional complex network theory, the node vulnerability analysis method based on nonlinear causal theory is more effective and accurate, providing a reliable basis for subsequent targeted protection of systems.