Abstract: By using the numerical simulation and formula fitting methods, the influence factors for the critical height of soil-nailing foundation pits are studied. The similarities between the influence factors and the critical height are analyzed. The results indicate that the critical height of soil-nailing foundation pits has some important influence factors, and some influence factors have certain quantitative relations with the critical height. The influence factors for the critical height of soil-nailing foundation pits are studied and analyzed. Fitting formulae between the main influence factors and the critical height are obtained. A new idea for determining the formula for the critical height of soil-nailing foundation pits is provided.