This paper is studying the Evaluation of the performance of reservoir facies of Yamama Reservoir in Ratawi oil Field which locats about 70 kilometers west of the city of Basra and to the west of the North Rumaila where away about 12 kilometers, and to the south of Hor Al-Hammar reality along the Euphrates River in Mesopotamia zone in Zubair subzone. The study includes a petrophysical evaluation performance of the reservoir by using several methods for each unit especially the three reservoir units comprising the Yamama Formation in four boreholes which are Rt-3, Rt-13, Rt-14, and Rt-15 distributed around the crest of the Ratawi structure that are carried out in the present study. Yamama formation boundaries were determined using well logs , available core intervals and Petrophysical data and found that it can be subdivided into three main reservoir units that separated by two insolate ( non – reservoir ) units. Petrophysical analysis of Yamama rocks revealed that YB unit has the best properties comparing with the other two units because the majority of effective porosity is primary through the whole succession within the studied area.