Film tension control in slitting or rewinding process means the ability to permanently control the tension of the film passing through the equipment. This tension control must remain valid for any operating speed no matter acceleration or deceleration, make sure without damage to film even in emergency braking. The stability of tension control is directly related to the product qulity. If the tension is insufficient, the film will drift in the running process, and the film coils become wrinkle. If the tension is excessive, the thin film is easily broken, result in lots of broken ends on coils after cutting and rewinding process. This article deeply analyses the problem of tension control for film winding.