Abstract: Aiming at the broblems that complex information systems have the high complexity,mutual influence and interdependence,and the existing risk assessment methods are difficult to adapt to large-scale network security risk assessment and application needs of practice,we researched risk factor analysis method and the overall risk assessment methods of complex information system based on GTST-MLD,including the study of complex systems model of accidents interdependencies,risk factors model and risk conduction analysis,which improves risk assessment capabilities and level of analysis for complex information system．The results prove that the model consolidates the security features of complex information system,such as objectives,functions,structure,behavior and so on,achieves security analysis at a higher level system functions,and provides a reliable means of quantitative analysis for complex information system risk assessment．

Key words: Complex network,Information security,Risk assessment,Interdependencies,Risk conduction