In order to acquire the functional dependency network analysis (FDNA) strength of dependency(SOD) parameter α and criticality of dependency(COD) parameter β, this paper proposed a method to analyze the SOD and COD parameters through adjacency matrix and reachability matrix. Based on the occurrence graph in Petri net, proposed formulas to calculate SOD and COD parameters, and the results are validated by the solving examples of the system of systems effectiveness SOD and COD parameters and its sensitivity analysis. The results show that the method is reasonable and feasible, which can make up the deficiency of the current FDNA application research.