Background & Aims of the Study: There are several methods for determining the water supply system safety, including the WSP program that recommended by the World Health Organization (WHO). So, the aim of this study was assessment the water supply system of Hamadan city based on the Water Safety Plan (WSP) guideline introduced by the world health organization in 2018. Materials & Methods: This investigation employed the WSP-QA Tool and the WSP manual of the WHO and the AWI in 2017. For this purpose, software checklists were prepared and, after confirmation of content and face validity, completed based on Hamadan water and wastewater company records and interview with company’s experts. Data was analyzed using WSP-QA Tool and then system hazards were identified and risk assessment and prioritized hazards were performed by use of semi-quantitative risk matrix approach presented by the WHO guideline. Results: The results showed that from the total score of 440 complete implementations of WSP and according to the 384 score related investigation different phases of this study, the 220 score was achieved that 50 % was coordinated with WSP. The Results of risk assessment showed that discharge wastewater from a village and agriculture in the catchment, blocked filter and algae in treatment, old pipe and excavation and installation facilities in the distribution and pressure drop and constructing wells at home in point of use are the most important hazards in water supply system of Hamadan. Conclusions: Overall, The results showed that the implementation WSP in Hamadan city is in a moderate situation
