Abstract: The top and bottom of many oil storage tanks are of spherical structure that is axially symmetrical. The calculation is so complex as it is done according to torque principle that the inner stress acquired is often vulnerable to mistakes, and therefore must be checked. This paper, taking a definite free body and based on balance conditions, infers the checking equations for calculating radial force, circumference force, transverse shear force as well as radial torque, and gives an example of calculation.