Various parameters such as type of feedstock, inlet and outlet coil temperature, heat flux and residence time, affect the performance of a thermal cracking reactor. The pyrolysis coil configuration is one of the most important parameters which affects the performance of the reactor.In this research the effect of four different coil configurations, namely single row, millisecond, split and reversed split have been studied on run length, product yields, outside surface temperature of coil, coke deposition as well as temperature and pressure distribution. The reactor under investigation is the thermal cracker of Abadan petrochemical complex which uses propane as feedstock. The results show that millisecond coil configuration has the highest yield of ethylene and lowest coke thickness. However, it exhibits the lowest run length and worst ratio of length to diameter conditions. On the other hand, single row coil configuration has the lowest ethylene yield and highest coke thickness but, the highest run length with the lowest pressure drop also belongs to this coil configuration. It also presents the most even distribution of pressure and a linear temperature profile across the coil length, favoring better selectivity.