The heights design principle of progressive addition lenses is described. A method is proposed to change the mean curvature to design and optimize progressive addition lenses by adjusting the main curvature difference. The designed and manufactured results of progressive addition lenses are compared, and the powers in effective usable portions are maintained before and after optimization. The intermediate widths of the optimized lens are 0.7 mm wider than those of the unoptimized ones. The areas of the effective visual region of the optimized lens are broader than those of the unoptimized lens. The maximum astigmatism reduces slightly. It is shown that the design and optimization method proposed meet the practical demands.