A modified temperature integral approximation formula was proposed to calculate the kinetic parameters of tire pyrolysis. The relative error percentage of our formula was less than 0.02% at the range of 5 <= u <= 80. In order to validate our formula, the kinetic parameters of waste tire pyrolysis in a Thermogravimetric Analyzer (TG) were calculated according to different temperature integral approximation formula. The results demonstrated that the coefficient of the experimental TG and simulated TG from our formula was higher than that from Coats-Redfern method. The active energies of tire pyrolysis were 33.03 (120-300 degrees C), 72.30 (300-420 degrees C), and 50.83 kJ/mol (420-500 degrees C).