The complex interactions are existed among logical nodes defined in IEC61850.The faults in substation automation system may further propagate via these interactions.Based on the perspective of complex network theory，the logical nodes are treated as networks nodes，the logical connections are treated as networks edges，complex relationships among logical nodes can be expressed as a complex network.First，the relevant statistic parameters of complex network are calculated.The results show that the interaction relations among logical nodes have the characteristics of small-world and scale-free at the same time.Then the cascading failure model of substation automation system is established based on coupled map lattices（CML）.Simulation results show that the model reveals the propagation rule of logical node failures in the system.Finally，the interactive features of the logical nodes in automation system of T1-1substation are analyzed，and the simulations based on the established model further validate the effectiveness of the method.