The polymerization kinetics of Fischer-Tropsch reactions on a cobalt-based catalyst was studied. A kinetic model was developed based on the alkyl and alkenyl mechanisms for hydrocarbon chain propagation that may occur simultaneously in the Fischer-Tropsch synthesis. The kinetic model comprised initiation of hydrocarbon chains, propagation, termination to paraffin and olefin and readsorption of olefin. The proposed model was validated by F-test and proved valid at a confidence level of 95%.