Aiming at the problem of how to estimate the horizontal bearing capacity of the pile foundation after the pre-reinforcement treatment, this paper establishes a simplified p–y method model with reference to the port engineering pile foundation code, and the limit horizontal soil resistance P_u=m(x+x₀) ⁿ power function of the clay was given. The balance differential equation of the pile body was established, through the parameter substitution method, the relevant analytical solution was given by the series solution theory of ordinary differential equation, giving The Matlab source code for the calculation of the relevant parameters is obtained. Finally, through the engineering case and the analytical solution newly calculated in this paper, it is concluded that after the soft soil foundation is pre-reinforced by vacuum preloading, the characteristic value of the horizontal bearing capacity of the pile foundation is changed from the original 51.6 N to 121 N, and its rationality is verified by comparing the test results of the pile foundation after pre-reinforcement treatment.