Abstract: Nitrite is a serious health hazard and exists widly in drinking water,foods,biological systems and agricultural products.Under acid conditions,AuNCs@BSA was found to be exclusively quenched in the presence of nitrite with a good linear relationship with nitrite concentration of 0.3 to 60 μmol/L,and the detection limit up to 32 nmol/L.In addition,the mechanism of sensitive fluorescence quenching response of nitrite with AuNCs@BSA under acid condition had been discussed,and the results revealed that the secondary-structure change of the capping ligand BSA played an important role in the emission quenching of AuNCs@BSA.The nanoprobe was used to detect nitrite in sausage,and the results were consistent with those obtained using a UV visible spectrophotometer,which confirmed that the proposed method was reliable and rapid in detecting nitrite residues in real samples.