The headstock is one of the most important parts of a machining center, however there are a lot of designing variables that may influence the static and dynamic capability of the headstock. How to find these variables and optimize them seems to be very important. In this paper, using the modal frequency as the performance index, Pro/Mechanical was used to analyse the sensitivity of the DVG850 high-speed vertical machining center headstock. The result of the analysis was a set of main design-variables that influence the first-order natural frequency of the headstock. The machine’s typical operating conditions were compared against the results of the sensitivity analysis. This provided a basis for structural design and optimization of the headstock directly and quickly.