This invention provides an optical imaging lens system in order from an object side to an image side comprising five non-cemented lens elements with refractive power: a first lens element with positive refractive power having a convex object-side surface; a second lens element with positive refractive power; a third lens element with negative refractive power, and both surfaces being aspheric; a fourth lens element having a convex image-side surface, and both surfaces being aspheric; and a plastic fifth lens element having a concave image-side surface, both surfaces being aspheric, and at least one inflection point is formed on at least one of the surfaces thereof. By such arrangement, the refractive power of the optical imaging lens system can be effectively distributed with improved light converging power so that the total track length can be shortened effectively, and the aberration of system can be corrected to facilitate high image quality.