Various aromatic compounds,including alkyl and halo benzenes,were nitrated to mononitro compounds in reasonable yields (40%-80%) with NH₄NO₃ from 0 ℃ to room temperature in Brnsted acidic ionic liquids with ［Hmim］［CF₃COO］ and ［Hmim］［HSO₄］ as solvent and catalyst respectively. The isomer ratios for nitration of toluene in Brnsted acidic ionic liquids were comparable to that obtained in mixed acid nitration. Isomer ratios for the nitration of halo benzenes in Brnsted acidic ionic liquids are different from that obtained in mixed acid nitration,usually,with higher para selectivity. The para-/ortho- product isomer ratio is 6.2 for the nitration of chlorobenzene at 18 ℃ for 8 h with n(TFAA)/n(NH₄NO₃)=5. The para-/ortho- product isomer ratio is 14.0 for the nitration of bromobenzene at 0 ℃ for 8 h with n(TFAA)/n(NH₄NO₃)=5. The para-product, p-nitrobromobenzene, from the nitration of bromobenzene in ［Hmim］［HSO₄］ under 0 ℃ precipitates with 98% purity, which facilitates the separation of the pure isomert.