Integrated Modular Avionics (IMA), which is the novel concept of avionics architecture, can effectively improve the efficiency of system while reducing resource allocation. However, it also brings new types of risk such as fault propagation since the flexible mapping between logical configuration and physics configuration. In some way, IMA could be regarded as a network where interdependency relationship between function and resource denotes the edge, function and resource denotes the node. Vulnerability and criticality of nodes are characterized by scheduling frequency and degree, for simplicity, redundancy is not considered. As a safety-critical system, IMA structure itself provides a potential route for fault propagation with the need of flexible resource scheduling. Effective modeling and risk assessment would help for the development bargaining or reconfigure strategy implementing. This paper provides a formal specification and risk assessment approach for integrated complex system and a case study in IMA domain is illustrated.