Cracking of Pyrolysis Fuel Oil (PFO) using a microwave plasma torch in liquid has developed a new process for production of valuable petrochemical hydrocarbons. Main parameters, including the power and flow rate of the carrier gases on the cracking operation were studied. The major products obtained were hydrogen and light C-1, C-2, C-3, and C-4 hydrocarbon compounds. Increasing of the power and gas flow improved the cracking of PFO, but, they were unable to change the selectivity of products. Optimal conditions were 850 W for power and 5000 sccm (ml/min) for flow rate and the production rate of C-4 and H-2 were 27.37 sccm and 446.31 sccm, respectively. (C) 2013 Elsevier B.V. All rights reserved.