Most of the analysis and calculation of soil stability is based on the formula from the two-dimensional theory, in order to solve the problem that it cannot take into account the effect of the pile hole circular arch in the space project Based on В. Г. theory and the principle of retaining wall, considering the soil arch effect on the stability of the hole wall, a calculation model for calculating the maximum hole depth of self-supporting hole wall was put forward. According to different formula solutions and the MATLAB numerical analysis software, the correlation coefficient in the model was adjusted several times. Finally a simplified calculation formula was proposed, the calculation formula and В. Г. formula solution were contrasted and analyzed. The result shows that this formula can calculate В. Г. theoretical solution for better approximation, which is more concise than the В. Г. formula, beneficial to the popularization and application, and more convenient for application in practical engineering.