A study was carried out for the effect of different levels of salinity i.e. (0,60 and 120mM (Nacl) and potassium levels i.e 0 and 30mM (k₂So₄) on growth and chemical composition of seedlings of two olive cultivars karotina and picwal during 2009 and 2010 seasons at Inshas Research Station, El-Sharkia Governorate, Water Management Research Institute, Egypt. The seedlings were grown in hydroponics system (nutrient film technique NFT).  Results revealed that, increasing salinity levels caused a gradually decrease in plant height, stem diameter, number of leaves/plant, number of branches/plant,  N, P and K percentages, while Na ,Ca and Mg percentages were increased gradually with increasing of salinity levels. Potassium addition increased in plant height, stem diameter, number of leaves /plant, number of branches / plant, N, P and K percentages, while Na, Ca and Mg percentages were decreased. The results revealed the necessity of potassium fertilizer to reduce negative effects of salinity on plant growth. Karotina cultivar gave the highest values of previous parameters than picwal cultivar and seems to be more than tolerate salinity compared with picwal cultivar.