In recent years due to rapid urbanization, industrialization, and modern agricultural activities, the quality of water bodies deteriorated causing environmental hazards. The present study was intended to calculate water quality index (WQI) of a perennial pond of Muzaffarpur, in order to ascertain the quality of water for public use and other purposes. The study was carried out for a period of one year. Water quality monitoring has one of the highest priorities in environmental protection policy. Water quality index (WQI) indicating the water quality in terms of index number, offers a useful representations for overall quality of water for public or for any intended use as well as in the pollution abatement programs & in water quality management. A number of parameters affect the usability of water for a particular purpose. In this study WQI was determined for the rainy, winter and summer seasons on the basis of various physic-chemical parameters such as pH, dissolved oxygen, total alkalinity, hardness, etc. Keywords: physic-chemical parameters, WQI, perennial pond, environmental hazards.