High speed milling (HSM) on inclined plane is the basic process of die and mould. The dynamic characteristics of the process are experimentally studied by changing the factors as inclined plane, cutting parameter and feeding mode on the high speed milling machine tool. The angles of inclined plane, spindle speed, feed amount and cutting depth are evaluated by the parameters of cutting forces and vibration. The feeding of projection process limits the milling vibrations mainly from horizontal (X) and (Y) directions. The cutting force reaches the peak value when the angle of inclined plane is 45°. The radial cutting depth shows more effects than the axial cutting depth to cutting force and vibration. However, the axial cutting depth should keep a minimum value when using ball mill.