Near-infrared fluorescent gold nanoclusters (AuNCs) were prepared by sonochemical method and applied for the selective and sensitive detection of nitrite. The fluorescence of AuNCs could be selectively quenched by nitrite, and the mechanism was discussed in detail. The fluorescence intensity decreased linearly upon the increasing concentration of nitrite in a wide range of 2.0×10(-8) M to 5.0×10(-5) M. The detection limit was only 1.0 nM (S/N=3), which was much lower than the maximum admissible concentration of 2.2 μM required by the European Community. The proposed method was also applied for the determination of nitrite in real water samples. The present method exhibited excellent analytical performances, such as wide detection range, good selectivity, high sensitivity, and the applicability in neutral medium.