Abstract: This paper presents the analysis of stress at the annular plate and bottom node of storage tank, is suitable for the case with the annular plates and center plates lap-jointed and with a concrete ring wall under the tank shell, and presents accurate theoretical analysis and stress calculations. This method can be compared with the API and ASC(Academy of Sciences of China)method to compare the suitability of their tank foundation hypothesis. For 5 000 m³ storage tank with its stress measurements carried out, the measured stresses are more than this paper's theoretical stress calculations and the calculations of Wu Tianyun method, are consistent with the results of ASC method, but are most discrepant with the API results. The difference among the methods is discussed, and so is the reason for those differences. The given equation group has ten variables with eight linear variables and two nonlinear variables, so this is a nonlinear equation group. The double area-bisection presented here is of universal significance for nonlinear equation groups with only a few nonlinear variables in them, and eliminates the inconvenience of Newton iterative method which needs the derivatives of all ten equations. This paper's method only solves linear equation group, so the plot of solving nonlinear equation group is ingeniously conceived.