In the present study, gas phase dielectric barrier discharge (GPDBD) was used for pretreatment of coking wastewater with the objective of improving its biodegradability. The effects of some operational parameters including initial concentration, pH value of coking wastewater and air flow rate in GPDBD reactor on the COD removal were investigated. The removal efficiency of main compounds (total phenol, PAHs and NH3-N) and biodegradability (BOD3/COD) of coking wastewater were evaluated. The results show that the removal of COD by GPDBD fitted well with the second-order kinetics. The raw pH of coking wastewater was beneficial for COD removal. The optimal air flow rate was observed as 2 L min(-1). Approximately 100% of total phenol and PAHs (benzoquinone, naphthalenol, dimethyl phthalate, etc.) removal was achieved at a reaction time of 120 min, and the removal efficiency of NH3-N reached 21%. The BOD5/COD ratio increased from 0.14 to 0.52 within 100 min of discharge treatment, suggesting the biodegradability of the coking wastewater was significantly improved. The GPDBD system is an effective pretreatment method for enhancing the biodegradability of coking wastewater. (C) 2015 Published by Elsevier B.V.