The present study was conducted to examine the effect of humic acid concentration (0, 0.5, 1 and 1.5 ml/L) and some of biofertilization treatments (control, Azotobacter chroococcum, Mycorrhizae (Glomus macrocarbium) and mix of Azotobacter chroococcum + Mycorrhizae on olive seedling which grown under three levels of saline water (2000, 3000 and 4000 ppm). this experiment was carried out during two successive seasons (2015 and 2016) on Olive seedlings Picual cultivars grown in El-Sheikh Zuwayid station, Desert Research Center North Sinai governorate, Egypt.Based on growth parameters data showed that salinity level (2000ppm) produced the highest significant parameters of the olive seedling; for seedling height, trunk diameter, Branch number., Leaf number., leaf length, leaf width, leaf area, and also the fresh and dry weight of shoot and root system. The lowest values were recorded for salinity level (4000 ppm through the two seasons. Salinity level at 2000 ppm gives the chance of growing plant to complete all of its physiological processes at a proper time than that of high concentration. Highest salinity concentration 4000 ppm caused a decline in all the studied parameters throughout both studied seasons. Increasing humic acid levels from 0.5 to 1.5 ml/L % increased significantly all studied parameters when compared with control (0) in the two studied seasons. Application of biofertilization treatments either singly or mixed enhanced growth and plant biomass of olive seedling under different salinity treatment. Mixed two types of biofertilzer had a significant effect on seedling growth than control and one type of biofertilizer treatments.In addition, Macronutrient content in olive seedling leaf positively affected with humic acid concentration and biofertilization treatments. Mixed biofertilization treatment resulted in higher values of soil microbiological properties, i.e. total microbial counts, Azotobacter densities, Mycorrhizal infection percentage, no. of mycorrhizal spores /gm, microbial enzymes in soil (Dehydrogenase, Nitrogenase and Phosphatase). It can be concluded that, to mitigate the negative impact of salinity of olive seedling we recommend to use humic acid (1.5 ml/L%) with the treatment of biofertilizer (Mycorrhiza and Azotobacter chroococcum).