This invention discloses a thin optical lens assembly, comprising two lens elements with refractive power arranged from an object side to an image side along an optical axis, a bi-convex first lens element with a positive refractive power, a second lens element with a negative refractive power having a concave object-side surface and a convex image-side surface, and an image sensor on an image plane. Each of the two lens elements has two aspheric optical surfaces, and preferably is made of plastic. Additionally, the thin optical lens assembly satisfies the conditions of the present invention in order to reduce the total length and the sensitivity for its use in compact cameras and mobile phones with photographing functions.