Abstract: This paper is concerned with the dynamic response of structures based on probability. By means of modal analysis, the numerical characteristics of structural dynamic response are formulated. The randomness of both physical parameters of structure and the amplitude peak of applied load are taken into account in the present model. Numerical examples are provided to examine the influence of the randomness of physical parameters of structure and the amplitude peak of loads on structural dynamic response. It is shown that the present model is reasonable and effective.