The experiment was carried out in two consecutive seasons (2017/18 and 2018/19) on ‘Sukkary' and ‘Gahrawy' mango root-stocks seedlings and the purpose of the research was to investigate the effectiveness of applying Nano-silica to increase the tolerance of ‘Gahrawy' and ‘Sukkary' mango rootstocks. The tested treatments were tap water irrigation (TWI),TWI and spraying Nano silicon (SNSi) at 1.0g/L,Sea water irrigation (SWI) at 1750ppm, SWI at 1750ppm and SNSi, SWI at 3500ppm, and SWI at 3500ppm and SNSi. Foliar sprays of Nano-silicon were done four times;the first at the beginning of the experiment, and then three times at 45-days intervals.The effect of treatments on the behavior of the seedlings of the two rootstocks including vegetative characteristics (new leaf area, seedling height increase%, seedling stem diameter increase, root length and width, number of lateral and secondary roots and root growth coefficient), physiological parameter "Leaf pigments, total phenols and soluble carbohydrates contents",leaf mineral contents " N, P, K, Na, Ca and Mg" and Non-enzymatic antioxidants"proline content and DPPH" as well as salinity symptoms parameters were studied. Increasing levels of salinity caused a decrease in most parameters and an increase in the sodium and proline content, and salinity symptoms of the leaves. Irrigation with salty water at 1750ppm together with foliar spraying Nano-silicon enhanced leaf content of pigments, soluble carbohydrate and total phenols, Mg, N, P, K and decreasing of salinity symptoms parameters.The results confirmed that the effects of Nano-silicon on the behavior of treated seedlings differ according to the variety under salinity conditions.