The paper is aimed to make a research on the dynamic load of ejector tube in the processing of engine testing on the basis of the frequency identification method. The author firstly measured The dynamic response of ejector tube in the processing of engine testing by experiments, then obtained the response of the structure activated by the basis function of load by FEM, finally got the result of the dynamic load of ejector tube by least squares method. The dynamic response of ejector tube activated by the identified dynamic load is also calculated and compared with the response of ejector tube in the engine testing measured by experiments. The error between the responses is obtained, and the cause of the error is analyzed. The result shows that the identification method in this paper can be used to identify the dynamic load of ejector tube in the processing of engine testing accurately, and it can provide a reference method for further engineering studies.