Studies of coke formation and deactivation kinetics during cottonseed oil catalytic cracking were carried out on a laboratory scale fixed-fluidized bed reactor. The chemical composition and the location of coke were investigated by using various analytical techniques, such as X-ray diffraction (XRD), infrared (IR), nuclear magnetic resonance (NMR), thermal gravity analysis (TGA), etc. The results showed that the coke deposited on the catalyst was mostly aromatic hydrocarbon. A new model for describing catalyst deactivation in cottonseed oil cracking has been used, and compared with a more traditional model based on coke deactivation; the reaction time can be regarded as an invented reactant in the new model.