Exhaustive indole oxidation in aqueous solution was studied using contact glow discharge plasma. The results indicated that the rate of indole degradation increases with the decrease in the solution conductivity. The degradation rate can be enhanced under the following situations. First, the increase in temperature. Second, introduce active carbon and hydrogen peroxide to the solution. Third, the degradation process is performed in alkaline or acidic media rather than the neutral media. Fourth, add Fe2+ to solution to undergo Fenton's reaction. However, n-butanol was found decelerate the degradation of indole. Some major intermediates produced during the degradation were detected by using both HPLC and GC-MS.