Most of water resources nowadays are exposed to pollution caused by domestic, industrial and agricultural wastewater. Pollution is also caused by climate changes, acidic rain, etc. The superficial pollution can infiltrate through soil into the underground water. The danger of this pollution depends on the nature, concentration and type of the pollutants. The main objective of this study is to evaluate and control the physicochemical quality of underground water of ALLAL TAZI- Gharb Morocco .The research is carried out on 22 underground water wells in the region under study. It analyses and controls 12 physicochemical parameters of the collected samples in ORMVAG Laboratory, Kenitra. These parameters are pH, EC, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, (NH4+) et NO3-, CO32- et bicarbonate HCO3-.The results have shown that the concentration of ammonium NH4+ in 95% of wells and nitrate NO3- in 68.2 % of wells are much higher than the World Health Organization (WHO) norms . This indicates that there is nitrogen pollution as a result of industrial and domestic organic waste or due to the excessive use of soil fertilizers. The electric conductivity in 31.8 % of wells, concentration of chloride Cl- in 41% of wells, and concentration of sodium Na+ in 31.8% of wells are relatively higher than WHO norms. This explains the existence of high level of mineralization in water-wells of the region under study as a result of geological structure or industrial and domestic pollution. The study has also revealed that other parameters are approximately in concord with the norms set out by WHO. It is concluded that the physicochemical quality of the underground water of the region under study is medium.