The settling curve of single pile with grain spillage under the effect of vertical static load was analyzed. The curve was divided into 3 parts: elastic line phase at the beginning, grain spillage tamping phase and elasticity breaking phase in the end, and the settling characteristics in three phases were described mathematically and the mathematical expression was concluded as well. Based on the calculation of the parameter with the optimizing calculation method, the parameter of “theoretical limit load” computing formula that satisfies the definition of limit load was presented. Comparing with the experimental result of the indoor single pile modeling, it is found that this parameter computing method is practical, which provides another method to predict the limit load and settlement of the single pile with grain spillage.