A rectangular optical glass lens and a manufacturing method thereof are disclosed. A rectangular glass blank is put between an upper mold and a lower mold of a multi-cavity mold and then being heated and pressured. The rectangular glass blank is molded into a lens sheet having a plurality of optical surfaces and the lens sheet is cut to form a plurality of rectangular optical glass lenses. The rectangular optical glass lens produced by such method includes two optical surfaces working as optical areas and a rectangle circumference on non-optical area surrounding the optical surface. The circumference is a rectangular part with four right angles on each corner while the right angles as well as the rectangular shape are formed by cutting of the lens sheet. Thus the manufacturing method of rectangular optical glass lenses are simplified and the produced lens is assembled with a lens module conveniently.