Application of methanol as a coreactant in the atmospheric catalytic cracking of refinery fuel oil (abbreviated as the MFOCC process) over the H-ZSM-5 catalyst has been investigated for the first time with the aim to improve the olefin productivity of the heavy hydrocarbons and mitigate coke formation and catalyst deactivation. The results clearly proved the synergistic influence of cocracking in the MFOCC scenario. The integrated MFOCC process increased both light olefin (C-2(=)-C-4(=)) yield and gasoline (C-5-C-11) share of the liquid products to more than 36.7 and 78.7 wt %, respectively. Influence of contact time and temperature was also discussed.