In order to optimize the action sequence of the functional components of the gantry machining center to improve production efficiency, the gantry machining center was structurally decomposed according to functions-movement-action, and its functional components action model was proposed based on the structured decomposition and the symbolic directed graph. In the model analysis process, Gantt chart technology was introduced to assist the design work of head change and tool change in the gantry machining center. The method of PMC control combined with macro program was adopted to realize the electrical control of tool change in the vertical and horizontal tool magazine with new actions. The action efficiency of functional components is improved.