High voltage pulsed discharge (HVPD) technology was utilized to degrade oilfield wastewater in order to improve its biodegradability. Water samples before and after treated were analyzed by GC-MS to investigate the mechanism of biodegradability improvement. The experimental results show that the BOD5/COD of oilfield wastewater can be improved from 0.066 to 0.33 after 10 minutes by HVPD treatment, the biodegradability of oilfield wastewater was improved effectively. The optimal operational parameters of this experimental are : the pulse voltage peak value is ±26 kV, the air flow rate is 0.50 m3/h and the pulse frequency is 150 Hz.The GC-MS analytic results indicate that the ploynuclear compounds and long chain alkanes and aromatic Hydrocarbons in oilfield wastewater are degraded to low relatively molecular pollutants after HVPD technology treatment.