This paper demonstrated the effects and influencing factors in degrading aniline by gaseous streamer corona plasma along water surface under different discharging gas atmospheres. For aniline with an initial concentration of 100 mg/L, the degradation was fastest when the reactor was not ventilated, and degradation rate is 98.5% under 7.5 min treatment. While the degradation was slowest when Ar was ventilated, the degradation rate is 98.6% after treated for 60 min. Some active particles were detected using a multi-channel fibre-optic spectrometer during the discharge, such as Ar, OH, N₂, N₂⁺ and N. In particular, NO was detected during air discharge. The NO and N₂⁺ could produce NO₃^- then generated nitric acid would affect the pH value of the solution. The intermediate products by N₂ discharge is nitrophenol, and nitrophenol would converted to p-benzoquinone. The O₂ discharge could produce an intermediate product of aminophenol. The intermediate products in Ar discharge were in small amounts and the final mineralization effect was the best.