SQM-NBD is a potent and selective AIE fluorescent probe. SQM-NBD exhibits excellent sensitivity to Cys and Hcy with the LOD of 54 nM and 72 nM, respectively.SQM-NBD has good cell permeability and low cytotoxicity. SQM-NBD has the potential for Cys/Hcy identification under physiological and pathological conditions.