Abstract: The pyrolysis characteristics and kinetic reaction models of vegetable tanned leather at three heating rates were studied based on iso-conversional method and generalized principal diagram method. Flynn-Wall-Ozawa and Friedman isoconversion method were used to calculate the pyrolysis kinetic parameters of untanned sheepskin and leathers tanned with different vegetable tanning agents. According to the results, the model was fitted. The composition of gases from the pyrolysis of vegetable tanned leather was analyzed by TG-FTIR-MS, and the pyrolysis characteristics and identification basis of vegetable tanned leather were discussed. The results showed that the main gases from vegetable-tanned leather during heating are CH₄, NH₃, H₂O, CO, HNCO, CO₂ and pyrrole. The occurrence of CO and the variation of CH₄ and NH₃ intensity could provide an identification of tannins in leathers. The generalized principal diagram showed that the pyrolysis process of vegetable tanned leather followed the random nucleation and nucleation growth mechanism model, and the average activation energy of tanned leather increased by different vegetable tanning agents.