A zoom lens system which includes a first lens group, a second lens group, and a third lens group, sequentially arranged from an object side of the zoom lens system to an image side thereof, and an aperture stop which is arranged between the first lens group and the second lens group. The first lens group and the second lens group have a positive focal length. The third lens group has a negative focal length. The second lens group is used for focusing. When the zoom lens system performs a zooming operation, the first lens group, the second lens group, the third lens group, and the aperture stop are moved along an optical axis toward the object side of the zoom lens system, such that a distance between the first lens group and the aperture stop, and a distance between the aperture stop and the second lens group increase, while a distance between the second lens group and the third lens group decreases.