Abstract: Random excitent testing and method of identifying modal paramenters for the model of a tall building are presented in this paper.First eight modal paramenters are gave and every three-dimensional mode shape is displied movingly on screen of Signal Processor 7T 17S and is copied.In addition we discussed how to ensure identifying precision of modal paramenters in the paper.The modal paramenters of the model obtaining from the tensting are able to use to verify dynamic calcunation method and to design the hight building.