Abstract: Dental unit waterlines (DUWLs) often experience severe microbial contamination. Opportunistic pathogens such as Pseudomonas aeruginosa and Legionella pneumophila present in DUWLs can enter patients′ mouths through procedural water, increasing the risk of infection during dental procedures. In response to the current situation of waterline contamination, this paper systematically reviews domestic and international guidelines, local standards, and industry requirements related to contamination control in DUWLs. It discusses five aspects were explored: incoming water quality control, tubing material, physical control measures, chemical disinfection, and microbial testing. The paper deeply analyzes and distills relevant strategies for waterline contamination control measures, providing a reference for infection prevention and control in dental practice to ensure patient safety.