Veterinary drug residues, particularly traces of β 2 -agonists, can cause various kinds of harmful impact to the environment and public health. Here, a sensitive chemiluminescence (CL) method incorporated with a flow injection analysis is developed for the determination of two β 2 -agonists [i.e., salbutamol (SAL) and terbutaline (TEB)]. The system is based on the CL reaction of Ni(IV) complex with luminol in alkaline solutions, whereas SAL and TEB can significantly enhance CL intensities. Under optimum conditions, CL intensities are proportional to the SAL and TEB concentration in the range of 1.0 × 10 −9 M to 5.0 × 10 −7 M and 1.0 × 10 −9 M to 1.0 × 10 −7 M, respectively. The limits of detection (3σ) are 1.0 × 10 −11 M for TEB, and 1.3 × 10 −11 for SAL respectively. Relative standard deviations (n = 11) are less than 2% for 5.0 × 10 −8 M SAL and TEB. Possible reaction mechanisms for the CL system are suggested based on the CL system spectra, Ni(IV) complex oxidation characteristics, and electron spin resonance (ESR) techniques. The proposed method has been applied to the analysis of urine and swine feed samples with satisfactory results.