The joint has a significant effect on the dynamic characteristic of the mechanism, and the identification of the stiffness of the joints has become a key problem. In this paper, a method is presented for identifying the dynamic characteristic of joints. An experiment is designed to test the dynamic parameter of the bolted joints specimen; the identification method, based on experiment, has a high accuracy result. By taking a specimen to experiment and identify the dynamic characteristic of joints, the relationship between the preload on the bolts and the joints stiffness is acquired. In order to validate the accuracy of the result, the FEM software is used to simulate. There are only a small discrepancy between the results of identification and simulation.