Abstract: Hydrodenitrogenation of indole and 1,2-dihydroindole were performed over a NiWS/γ-Al₂O₃ catalyst in a continuous fixed-bed microreactor; the effects of H₂S, quinoline and its hydrodenitrogenation intermediates on the hydrodenitrogenation of indole were investigated. Compared with indole, 1,2-dihydroindole exhibits obvious self-inhibition effect on the hydrodenitrogenation. H₂S can promote C(sp³)-N bond cleavage in 1,2-dihydroindole and slightly inhibit the hydrogenation reaction and C(sp²)-N bond cleavage in o-ethylaniline due to the competitive adsorption these species. The conversion of indole and denitrogenation efficiency are decreased seriously by adding quinoline into indole, indicating that quinoline inhibits the hydrogenation reaction pathway and C-N bond cleavage. This can be attributed to the stronger adsorption of quinoline and its intermediates such as 1,2,3,4-tetrahydro-quinoline and 5,6,7,8-tetrahydro-quinoline than that of indole.