Surface and groundwater are the main sources of water supply in Libya. This study aims to assess the water quality index for drinking and irrigation purposes. 15 surfaces and 47 groundwater samples are collected in an area where lies in Al Jabal Al Akhdar region, northeast Libya. Water quality parameters such as temperature (T), pH levels, EC, TDS, TH, TAK, major cations ( Ca2+, Mg2+, Na+, K+ and NH4+) and major anions (Cl-, PO43-, HCO3-, NO3-, SO42- and NO2-) were measured. Water quality indices including SAR, % Na, RSC, PI, MH, Kelly’s Ratio and PS were also computed. Main water types were classified based on Piper trilinear diagram. The results revealed a basic pH level for surface water with a maximum level of 7.88. In addition, it is also exhibited a basic pH level for groundwater in the wet season and changed from acidic to basic in the dry season with a maximum level of 8.1. This indicates high-level concentrations of bicarbonate in water samples as measured. It observed that the ratio between TDS and EC increased with the decrease of pH levels, which indicates more releasing inorganic matter. Calcium and sodium are the dominant cations while Bicarbonate and sulfate are the dominant anions in water samples. Based on the U.S salinity, the Wilcox, and the Doneen classifications, the obtained results revealed that the surface water is suitable for drinking and irrigation purposes. Meanwhile, the groundwater is classified between excellent and doubtful except for some samples that were classified as unfit for irrigation purposes. Furthermore and based on the Piper diagram, the water types are classified as calcium sulfate, sodium chloride and as calcium bicarbonate. The water statuses categorization, based on the computational method of water quality index for drinking and irrigation agree with that concluded by US salinity, the Wilcox, and the Doneen diagram.