To further realize lightweighting of the tank bottom structure of liquid launch vehicle tanks, a parametric approach is proposed by considering the load characteristics of existing tank bottoms (thickness parameters and the theoretical relationship with internal pressure during rocket operation) under actual working conditions. The residual strength coefficient is proposed as a design load index of the storage tank bottom, and a design criterion of the tank bottom thickness is established by combining the working conditions. When the residual strength coefficient is not less than 1, the tank bottom thickness is considered satisfactory, meeting the engineering needs, and the thickness of the tank bottom is optimized based on this criterion. According to the design criterion, the relationship between the opening and the bottom thickness can be established, and the critical thickness value of the bottom of the storage tank can be determined more accurately. The established bottom thickness design criterion can be used to verify the internal pressure bearing capacity of the designed storage tank bottom. The usability of the design criterion is validated by using actual working condition data, and a thickness partitioning and lightweighting method for spinning-type tank bottom is proposed. In addition, a multi-constraint evaluation model for the opening of the tank bottom is established based on the interaction of the inputs and outputs of the piping and sensor interfaces of the tank bottom. The specific practicality of the method and automated modeling are realized through a parametric platform. The results show that the thickness partitioning lightweighting method for spinning-type tank bottoms can realize an average weight reduction of about 30% for tank bottoms. The parametric platform and automated modeling provide a new method to improve the efficiency of storage tank bottoms.