Single crystal silicon wafer is widely used as the substrate material for integrated circuits, and the wafer is cut by wire saw with fixed diamond abrasive owning to the wire saw’s narrow kerf, low cutting force. The cutting force changes during the process operation since the wire change motion direction continuously (i.e., reciprocation) in order to effectively leverage the wire, even if the contact length of wire and part and wire saw tension are fixed, leading to wire saw breakage, wafer collapse, and inferior surface roughness. This paper established the model of cutting force that includes normal force and tangential force, and design the controller for regulating the force via wire velocity control, and the controller obtains the relationship between the normal force and commanded wire velocity. A PI controller experimental studies for Single crystal Silicon wafer wire saw machining are conducted. The results show the controller can well regular the cutting force generated when wire saw machines silicon and on that the wire saw machining process with PI control can decrease wafer surface roughness as compared to the cutting process with a constant wire velocity reciprocation.