Background: The best way to assure the quality of drinking water is implementing a comprehensive and integrated management system with cooperation of all the related organizations Therefore, the purpose of this study is the ASSESSMENT of SAFETY in drinking water supply system of Zanjan.Methods: This investigation was performed by WSP-QA Tool software and WHO and IWA manual of water SAFETY plan on water supply of Zanjan city in 2016. For this purpose, software checklist (containing 85 questions) were provided and completed according to the history of Zanjan Water and Wastewater Company and interviewing the experts of this company.Results: Data indicated that from all phases investigated, 52.95% was adjusted with WSP.System Description with the highest score, showed highest percentage of adjustment with the water SAFETY plan (100%) and the phase related to verification and control with the lowest score, showed lowest percentage of adjustment with the water SAFETY plan.Conclusion: Meanwhile, water distribution system is provided with a relatively average SAFETY level and there is the potential of various pollutions caused by identified risks in water distribution system, therefore changing the present approach is suggested.