Effective prediction and reasonable control of soil deformation and settlement caused by tunnel excavation and reduction the impact on surrounding soil and buildings have important significance for actual production. The stochastic medium theory simplification formula is used, based on the monitored surface subsidence of the west line of Shanghai South Hongmei Road Tunnel. The tunnel section convergence area ΔA and the tangent value tan β of the main influence angle are obtained by back analysis. The relationship between buried depth or relative depth and the two key parameters are studied. The results showed that the calculated values are in good agreement with the measured values. For shallow buried tunnels, the value of ΔA is larger and more discrete. With the increase of tunnel depth, when the buried depth of the tunnel is greater than 20 m, the value of ΔA is stable, most are between 0.2 and 0.4 m2. As the buried depth or relative depth increases, tan β generally shows an increasing trend, and the buried depth substantially satisfy the relationship of tan β=0.035z-0.098.