To keep pace with development of stone masonry dam construction and standardize the design of stone masonry dams， Design specification for stone masonry dams （SL25-91） is revised to this Code so that the stone masonry dam design could be safe and applicable， economically viable， technology updated and quality ensured. This Code is applicable to the design of Class 2 and Class 3 masonry dams for large and medium water resources and hydropower projects or Class 4 and Class 5 masonry dams over 50m high. It may also be used as a reference for the design of other masonry dams.