The aim of this study was to determine the influence of some environmental factors on dairy production of the 6307 Holstein cows raised in private farms which were affiliated to an agricultural cooperative "COPAG", in Souss-Massa region in south-West of Morocco. The results of the analyzed data of dairy control of these cows, collected between 2008 and 2012, were 6578.30+_1619.06Kg, 7034.88+_1842.07Kg and 325.10+_42.96 days, respectively, for 305- days milk yield (305-dMY), Total milk yield (TMY) and the Lactation length (LL). The rank of lactation (RL), the year of calving (YC) and the calving season (CS) had very highly significant effects (P<0.001) on 305-dMY, TMY and LL. However, the analyzed effects of calving age (CA) were non-significant (P>0.05) for all the studied parameters. The dairy production of the Holstein in semi arid climate showed a great variability. The effects were highly significant, regarding, the year and the season of calving. The production in the cold seasons was great rather than the hot ones, which confirmed a high sensitive to seasonal variations.