The purpose of this study was to evaluate the physico -chemical quality of oil mill wastewater (OMW) in four different regions of Morocco (Oued Jdida El Mhaya, Route de Rabat and Sidi Bouzekri).A comparative study has been studied with several samples of OMW from two processes of extraction of olive oil (semi- modern and continuous). The results of the physicochemical analyzes showed that the four regions has an acidic pH which is the average value of 5,478 + 0,254 and the conductivity values vary between : 4,620 and 11,500 (mS/cm). They are rich in organic matter. This parameter is expressed by the COD and BOD5 of which the average of all samples respectively is (39.095+17.397 gO2/L) and (101,033 + 33,122 gO2/ L, the acid is (1,402 + 0,197). The statistical study gave us the variance percentages 45,44 % to 30,77% for F1 and F2 whose total information is estimated at a percentage of 76,22%. Cartesian diagram enabled us to identify four groups and confirm that the station S1 is the most polluted of the four sites studied.