Abstract: A method based on response coupling substructure analysis (RCSA) was employed to study the frequency response function of tool center point (TCP) in the whole workspace of machine tools. Firstly, the dynamic models of the spindle and the bed substructure of the machine tool were established respectively, and the frequency response function of the joint of the substructure was deduced. Then, the dynamic characteristics of machine tool TCP were obtained by RCSA method according to the deformation coordination relationship and force balance condition of substructure joint. Taking VDF850 vertical machine tool as an example, RCSA method was used to calculate the dynamic flexibility amplitude and frequency response of TCP when spindle was at the top of Z axis, and the results were compared with those of finite element method of the whole machine. The results show that the dynamic flexibility amplitude-frequency response trends of the two methods are basically the same, which verifies the feasibility of RCSA method. Moreover, RCSA method avoids solving large-scale matrix eigenvalue equation of the finite element method of the whole machine, and improves the computational efficiency.