Ultra-precision flying cutting machining with a vertical milling style is an important means of ultra-precision machining. It has a close relationship between the machining accuracy and the dynamic characteristics of the aerostatic spindle. The film force acting on the spindle rotor is related to the manufacture, installation and static unbalance or dynamic imbalance or other factors. Therefore, it is necessary to analyze the dynamic pressure force caused by these factors in order to study on the rotor posture and quantitative movement of the spindle. This article derived the solution formula for the dynamic pressure reaction force of the ultra-precision machine tool spindle with vertical static film based on the basic theory of the rigid body dynamics. The gyroscopic torque of the spindle has been analyzed under different conditions with the spindle dynamic balancing tests, which provide a reference to the further analysis of the spindle dynamic characteristics.