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The degradation of phenol by pulsed discharge plasma above liquid surface (APDP) and under liquid surface (UPDP) was compared. The effects of discharge voltage, discharge distance, initial solution conductivity and initial pH on the phenol removal were studied. It was concluded that the phenol removal increases with increasing discharge voltage and with decreasing discharge distance in both APDP and UPDP system. The increase of the initial solution’s conductivity has a positive effect in the APDP system but has a negative effect in the UPDP system. In addition, the alkaline condition is conducive to the degradation of phenol in the APDP system, while acidic condition is conducive in the UPDP system. Free radical quenching experiments revealed that •O2- has an important influence on the degradation of phenol in the APDP system, while •OH plays a key role in the UPDP system. This paper verifies the differences of the two discharge methods in terms of phenol removal.