Receptancecoupling substructure analysis (RCSA) techniqueis the major approach to obtain tool point frequency response functions (FRFs) of machine tools, and its precision is primarily controlled by the end FRFs of each substructure and the parameters of each interface between two substructures. Currently, there isn’t a mature algorithm in the identification of the parameters at each interface. Therefore, transfer matrix and RCSA are used to predict tool point FRF, and PSO algorithm is used todetermine the connection parameters at the spindle-holder and the holder-tool interfaces by minimizing the difference between the predicted and measured tool point FRFs.Comparison between the predicted and measured results shows a good agreement and demonstrates that the identification method is valid in the recognition of the connection parameters at the spindle-holder and holder-tool interfaces.