A mold assembly for manufacturing an optical lens includes an upper mold and an upper mold core accommodated in the upper mold. The lower mold and the lower mold core contained in the lower mold. The upper mold core has a bottom surface, and the bottom surface is adapted to the top shape of the optical lens. The lower mold includes a base and a replacement mold core accommodated in the base. A cavity is recessed in the middle of the upper surface of the replacement mold core. The shape of the cavity is adapted to the shape of the bottom of the optical lens, and the replacement mold core is provided with positioning holes adapted to the foot position of the optical lens. In the present invention, a replacement mold core is formed on the lower mold, so that when the customer needs to change the position of the foot of the optical lens, only the replacement mold core of the mold assembly needs to be replaced. There is no need to replace the entire mold equipment, thus saving the cost of mold development.