Abstract: An interface-layer element and equivalent elastic modulus optimization method is presented and used to update structural models assembled by sleeve-bolt type of joints. Based on the study of a structure assembled with one joint, the identified equivalent elastic modulus of single joint was used directly in the structure assembled by three joints of same type. Thus, the model of whole assembled structure was improved. To obtain a better improved model, further model updating was performed to update each of the three joint interface-layer equivalent modulus. By updating the joint model using above method, the accuracy of the structure model and dynamic analysis could be improved significantly. It could be concluded that the presented method is efficient and effective, and it could be applied to either single joint or multi joints assembled thin-walled structures.