A zoom projection lens system, in order from the magnification side to the minification side thereof, includes a first lens group with negative refraction power, a second lens group with positive refraction power, a third lens group with positive refraction power, a fourth lens group with negative refraction power; and a fifth lens group with positive refraction power. The first, second, third, fourth lens group are movably positioned, and the fifth lens group is immovably positioned. The first lens group includes a first aspherical plastic lens. The second lens group includes a second aspherical plastic lens. The fourth lens group includes a third aspherical plastic lens. The system satisfies the formula: −2.4≦Fa1/Fw≦−2.1; 2.9≦Fb1/Fw≦3.2; −3.8≦Fa2/Fw≦−3.6, wherein Fa1, Fa2, Fb1 are the effective focal lengths of the first, second, third aspherical plastic lens respectively, Fw is the effective focal lengths of the system in a wide angle state.