In order to realize the quantitative estimation of tire vertical force, the algorithm of heavy-loaded tire vertical force estimation based on circumferential strain analysis is studied. A finite element analysis model of 16.00R20 tire is established. A comparison of tire loading test and modal vibration test indicates that the vertical stiffness error and vibration frequency error of the model are less than 7.79% and 5.49% respectively, which verifies the validity of the model. Using the finite element method, the influence of vertical force on tire grounding characteristics and circumferential strain of inner liner is studied. The characterization index of tire contact angle is proposed and verified by circumferential strain analysis, and the errors of the three indexes are all less than 8%. Taking the grounding angle and grounding length as identification features, the vertical force estimation model is established by combining grey wolf optimization (GWO) and the support vector regression (SVR), and the estimation accuracy is verified by finite element simulation. The results indicate that the characterization index in combination with the of characteristic point spacing angle of zero-order, first-order and second-order derivative of strain curve can accurately estimate tire contact angle. The error between the estimated value of the vertical force estimation algorithm based on GWO-SVR and the finite element simulation value is less than 1.8%.