Gas oil pyrolysis reaction and coke-formation with coking-inhibitor YZS1 has been studied. A pyrolysis kinetics model of gas oil with added coking-inhibitor YZS1 is developed by considering the influence of coking-inhibitors upon the reaction kinetics of pyrolysis and developing a new reaction scheme of pyrolysis. Ethylene

propylene and aromatics are proved to be as the coke precursors in the pyrolysis of gas oil. A simplified coke-formation kinetics model of gas oil pyrolysis is proposed and its kinetic parameters are estimated.