A simulation model for the pyrolysis of Orimulsion at 500-1200 degrees C was developed based on previously obtained experimental results. The pyrolysis could be divided into two steps : the first step was the primary reaction, and the second was the secondary gas phase reaction. The primary reaction was completed almost instantaneously and a large amount of tar was produced by the devolatilization reaction. The secondary reaction was much slower than the primary reaction, and it controlled product distributions and selectivity. Nine reaction paths taking into account the changes of 11 products of C10H20, C10H8, C6H6, C4H8, C2H4, CH4, CO, CO2, H2O, H-2, and coke were formulated. Some of the kinetic parameters of the reaction path network were obtained from the literature, and the other kinetic parameters were determined by fitting the simulated curves with the experimental data. The simulation model developed using the information was successful in calculating the complicated product distribution.