The pyrolysis characteristics of the cooking oil tar in an ambient air were investigated using a thermogravimetric apparatus with infrared-spectrum analyzer. Experimental results showed that the combustion process of cooking oil tar can be divided into five stages. The first step of mass loss is due to water evaporation. The second stage is the volatilization and combustion of the low boiling point compound，the third stage is the combustion of instauration hydrocarbon，the fourth stage is the combustion of ester and the last stage is the combustion of saturation hydrocarbon. A simple kinetic description, named in this work as ‘First Order Reaction and Three-dimensional Diffusion Separate-stage Model (O1+D3)’ model, was developed based on the experimental results and integral analysis method.