A ship will be subjected to the comprehensive effect of dynamic load, static load and sudden load (such as collision load) during the operation, resulting in the extremely complicated force distribution of the saddle of the LNG fuel tank. The determination of the force distribution of the saddle is therefore critical for the design and installation of the saddle of the LNG fuel tank. A calculation method for the saddle load superposition has been proposed by studying of the force between the C-type independent fuel tank and the saddle for the dual fuel ships, combing of IGF rules and the "Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk" of CCS. This method solves the design problem of the saddle and the surrounding structure. The key points for installation are given to provide technical references for the design and the installation of this type of spherical tank's saddle.