The invention discloses a zoom lens which comprises a first fixed lens group, a zoom lens group, a second fixed lens group, a focusing lens group and an optical filter which are sequentially arranged from an object side to an image side along an optical axis. During focusing, the zoom lens group and the focusing lens group respectively move along the optical axis, and the zoom lens further satisfies the following conditions that 1.32 <= FA / FC <= 1.97, -0.9 <= FB / FC <= -0.18, 0 <= FD / FC <= 1.1, wherein FA is the focal length of the first fixed lens group, FB is the focal length of the zoom lens group, FC is the focal length of the second fixed lens group, and FD is the focal length of the focusing lens group. The lens has excellent confocal imaging capability under visible light and infrared light, has a temperature compensation function, does not need to focus again during day and night switching, is clear in imaging, small in size, large in image plane, wide in application range and low in cost, and can be matched with various types of camera equipment to meet various the use requirements.