Proposes a network security situational awareness model based on Bayesian method, and analyzes the research status of NSSA model at home and abroad. Analyzes historical monitoring data and obtains prior probability, and then constructs the time-series model for the process of time, applies Bayesian method to process the data, combines the historical statistical data with monitoring data and conducts the effective safety prediction. On the network structure construction, uses a hierarchical structure and coordinates a reasonable evaluation system for the model accurately, fast and reasonable prediction of network security, and the model has better real-time performance.