UV/chlorine process was employed to treat polluted water containing alanine（Ala），and the volatile disinfection byproducts（trihalomethanes and haloacetonitriles） generated during the process were determined and analyzed. The effects of chlorine dosage，pH，UV radiation time，concentrations of bromide and ammonia ions on the formation potential of disinfection byproducts （DBPs） were investigated. The results showed that trichloromethane （TCM） and dichloroacetonitrile（DCAN） were produced after UV/chlorine process, and the concentrations of TCM and DCAN reached the highest values of 20.37 μg/L and 34.17 μg/L at 15 min, respectively. Lower [Ala]/[Cl2] molar ratio, longer UV radiation time, and neutral pH can reduce the production of TCM and DCAN, and the optimum conditions in this experiment were as follows: [Ala]/[Cl2] = 1 ∶ 2，UV irradiation for 2 h, and pH= 7. Besides, the presence of bromide ions can form bromochloroacetonitrile (BCAN) during UV/chlorine process, which increased the types and toxicity of DBPs, while the existence of ammonia produced fewer DBPs when compared with the ammonia-free solution. Different processes were also compared, UV irradiation alone did not produce DBPs, and the yield of TCM for chlorine alone was lower than that of UV/chlorine, but the yield of DCAN was greater than that of UV/chlorine. Finally, a possible pathway for UV/chlorine treatment of alanine to generate DBPs was proposed below: first, the hydrogen on the nitrogen atom of alanine was attacked, followed by decarboxylation and deamination to produce acetaldehyde and acetonitrile, and finally a series of substitution and hydrolysis reactions to produce dichloroacetonitrile and trichloromethane were performed. The aforementioned results can provide a theoretical basis for the application and popularization of UV/chlorine process.