The invention discloses a telescope zoom lens. A first lens group, a second lens group, a third lens group and a fourth lens group are arranged from an object side to an imaging side sequentially along an optical axis, and the refraction capacities of the first lens group, the second lens group, the third lens group and the fourth lens group are positive, negative, positive and positive respectively. The first lens group is fixedly arranged at a first specific position, the second lens group moves back and forth along the optical axis following the changes of the amplification power of the zoom lens, the third lens group is fixedly arranged at a second specific position, and the fourth lens group moves along the optical axis to keep an imaging plane produced by the zoom lens being accurately projected on an image recorder. Therefore, the amplification power of the zoom lens can reach 20 times (X), in a zoom process, the first lens group and the third lens group are in a condition of rest, and only the second lens group and the fourth group move.