The source Ain Moulay Yacoub Hamma located upstream of Oued Hamma (Outita : pre-rifaine ride) 18 km southeast of the city Sidi Slimane, presents non-permanent flows during the three months February, March and April of the year 2017. The objective of this study is to evaluate the quality of the natural waters of Ain Moulay Yacoub Hamma, the hydro-chemical facies and the origin of their mineralization.Sampling is carried out at the source of these natural waters in order to carry out physico-chemical analyses in our specialised laboratory. As a result, the study showed that the waters of the Ain Moulay Yacoub Hamma spring are meso-thermal waters (42°C), with a poor quality sulphurous odour loaded with mineral salts (chlorides, sodium and sulphates). In the results presented in the Piper, Schoeller and Stiff diagrams, show that these waters are characterized by a chloride sodium chemical facies.