The combustible material of fire in fog discharge pipe is the cooking oil tar. Cooking oil tar was conducted on a specially designed laboratory-scale thermobalance (Macro-TG) with sample loading of 15g under dynamic air atmosphere. The effects of heating rate (5, 10, 15, 20 and 25°C/min) was examined. 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. Experimental results shows that large amount of sample has a pyrolysis reaction retardancy. The distributed activation energy model was used to study the pyrolysis kinetics. Science the reaction occurred in small activation energy told us that if the cooking oil tar put on fire it will be spread rapidly and hard to put out.