本文采用以模态迭加原理为基础的实模态分析技术及初参数优选法对汽车车架的模态参数进行了识别,讨论了振动特征值问题中关于非重特征值和重特征值的矩阵摄动法,提出了利用有弹性元件悬挂的结构振动测试数据来得到自由——自由结构的模态参数的摄动修正方法.文中还给出了一些数值例子来说明此方法的应用,同时得到了一些重要结论. In this paper, the real modal analysis technique based on modal superposition principle and the method of initial parameter optimization are used to identify the modal parameters of the automobile frame. The matrix of non-eigenvalue and eigenvalue in the vibration eigenvalue problem is discussed. Perturbation method is proposed to obtain the perturbation correction method of modal parameters of free-free structure by using structural vibration test data with elastic element suspension. Some numerical examples are given to illustrate the application of this method and to obtain Some important conclusions.