This study described a novel electrochemiluminescent (ECL) competitive immunoassay for ultrasensitive determination of the beta-adrenergic agonist salbutamol (SAL) using CdSe quantum dot (CdSe QDs) and enzymatic amplification. Thioglycolic acid (TGA) capped CdSe QDs were immobilized on a glassy carbon electrode (GCE) with the help of chitosan. Then SAL coating antigen was linked to the surface of the GCE by using glutaraldehyde. In the presence of SAL standard solution, the immobilized SAL coating antigen competed with SAL solution for the limited binding sites of the antibody. With the increase of the SAL concentration, the antibody combined with SAL standard solution was washed away and the amount of immobilized HRP decreased. The electrochemical detection was based on the HRP catalyzed hydroquinone (HQ) to consume the co-reactant H2O2 generated in situ, which amplified the decrease of ECL intensity. Under optimized conditions, ECL intensity changed linearly with the logarithm of SAL concentration in the range of 0.1-1000 ng/mL with the detection limit of 8.4 pg/mL (S/N = 3). The ECL immunosensor possesses high sensitivity, satisfied reproducibility and selectivity, and extends the application of QDs-based ECL to immunoassays of beta-adrenergic agonists. (C) 2015 The Electrochemical Society. All rights reserved.