Characteristics of pulsed corona discharge were investigated experimentally to combine methyl radical decomposition and hydrodeoxygenation reaction for bio oil upgrading. In contrast to conventional upgrading methods, no hydrogen was used as a feed. The required hydrogen was generated in situ considering the ability of plasma to decompose methyl radicals to hydrogen. Pin to plate corona discharge and 4methylanisole as a model of bio oil were used. Effect of operating and design parameters namely, carrier gas flow rate, pulse repetition frequency, plate electrode diameter, pin number and gap distance were studied on the conversion and selectivity of products. Variation of mentioned parameters can alter the electron and energetic species density and energy which results in improving reaction conversion and product selectivity. The upgrading mechanism of 4ethylanisole was described by a reaction pathway. Demethylation, transalkylation, hydrogenolysis, demethoxylation and methane decomposition are the main chemical reactions. It is worth noting that the optimum condition for methyl decomposition and hydrodeoxygenation reaction are similar for most of design and operating parameters. It was found that the most valuable and abundant products were BTX and phenol with maximum selectivity of about 15% and 46%, respectively. Results indicated that corona discharge plasma can overcome the disadvantages of conventional upgrading process which caused by high pressure hydrogen. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights