The existing testability modeling and analysis methods of hierarchical electromechanical system have the defects of small testability parameters, in order to solve these problems, a new testability modeling and analysis method based on improved bond graph for hierarchical electromechanical system is proposed. The improved bond graph method is introduced, which is effectively integrated into Bayesian network. On this basis, the testability model of the system is built, and the testability parameters are obtained by interpolation. Taking the built system testability model as a tool, the structure of hierarchical electromechanical system is described, the bond graph of hierarchical electromechanical system is constructed, the fault of hierarchical electromechanical system is detected and isolated, and the testability modeling and analysis method of hierarchical electromechanical system based on the improved bond graph is realized. The experimental results show that: compared with the existing three testability modeling and analysis methods for hierarchical electromechanical system, the proposed testability modeling and analysis method for hierarchical electromechanical system greatly improves the testability parameters, which fully shows that the proposed method has better testability effect.