According to the distribution of gas fields in the western part of the northern continent of the South China Sea, in order to increase the production of gas fields more economically and green, it is necessary to add a riser to connect the two gas field platforms. Therefore, the leg structure supporting offshore platform jacket is taken as the research object. Seven sets of composite backpack pipe clamps are used to install the riser. Considering the actual loading conditions of the leg structure, the strength and buckling stability of the jacket leg structure are analyzed when the pipe clamps are at different positions. With the help of the constructed SACS calculation model, the safety and reliability of the strength and buckling stability of the jacket leg structure were verified when seven sets of composite backpack pipe clamps are used under the water depth of 88 meters of the offshore platform, which provides a reference for the design of the platform leg structure under the same working environment.