Response surface method was used to study the effect of aromatic extraction of heavy feedstock in thermal cracking. N-methylpyrrolidone as the solvent performing dearomatization of feedstock was at different temperature and molar solvent to oil ratios. Temperature, flow rate and steam-to-hydrocarbon ratio were in the range of 1,053-1,143K, 1-2 g/g, and 0.75-1.2 g/min, respectively. From the CCD studies, the effects of flow rate and coil outlet temperature were the key factors influencing the yield of light olefins. Ethylene and propylene yields increased more than 10% by dearomatization. C5 + decreased by 13% on average. Finally, we obtained the single maximum yield of ethylene, propylene, and simultaneous maximum yields for untreated and raffinate.