With the development of aviation industry, higher requirements are placed on the reliability and precision of aerospace components. Hydrostatic bearing technology is widely used in the aviation field. In this paper, the static pressure guide rail is taken as an example to study the calculation method of the bearing capacity of the static pressure bearing cavity, so as to obtain more accurate oil cavity bearing capacity, and then prepare for improving the reliability and precision of researching aerospace components. At present, the method called “Translating External Load” is generally used to analyze the bearing capacity of the oil pocket. Since the mechanics model of “Translating External Load” method varies with the variation arrangement of the oil pocket, so “Translating External Load” method has less commonality. According to the principle of superposition of force and the idea of converse thinking, the bearing capacity of the oil pocket with constant flow supply is divided into six parts, each part bearing the component of external load, and the mechanics model can be established. Based on the mechanics model built, the equation of the bearing capacity of each oil pocket can be derived with each load component acting on the hydrostatic slide. When the arrangement of the oil pocket is complicated, the computation of bearing capacity turns into the problem of statically indeterminate. Referring to the solution method of “Elastic Body”, the compatibility equations of deformations of oil film are presented, the statically indeterminate problem is translated into statically determinate problem, and the bearing capacity of each oil pocket is obtained. Vector superposition is carried to the six bearing capacity components of each oil pocket, and then the final equations calculating the bearing capacity of the oil pocket can be attained. The research work offers the general method for calculating the bearing capacity of the oil pocket, and the equations can be solved with the help of the computer programs and can improve the design efficiency and accuracy.