Objective In order to clarify the health risk of exposure to antibiotic residues via drinking water, this paper studied the baseline levels of antibiotic residues in drinking water of a city in Guangdong Province and the reduction effects of water treatment technology on antibiotic residues. Methods A total of 50 samples, including raw water, flocculation effluent, precipitation effluent, filtered water and finished water, were collected from 10 drinking water enterprises in a city of Guangdong Province. The occurrence of 92 antibiotics in water samples were detected using online solid phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry. Results The detection rates of antibiotic residues in 5 groups of samples ranged from 0 to 60%, and the sulfonamides were the major detected antibiotics. Therein, a total of 20 antibiotic residues were observed in raw water, primarily including sulfonamides, macrolides, quinolones and chloramphenicol antibiotics, with the concentrations ranging from 0.057 to 181.419 ng/L. The occurrence of antibiotic residues and their concentrations observed in the samples of raw water from river were higher than those from reservoir. The water treatment process effectively removed the antibiotic residues from raw water, the removal rate is 39.89~78.85%. Consequently, the antibiotic residues were mostly undetectable in finished water samples. However, the antibiotic residues still be detectable in finished water when river water was used as raw water. For the exposure assessment, the results showed that the population was posed toposed a higher risk of being exposed to antibiotics through this drinking water. Conclusion High level of antibiotic residues is observed in drinking water sourced from river water in a city of Guangdong Province, attention should be concerned to the potential risk associated with this finished water.