Two lysimeter experiments were conducted at Sakha Agric. Research Station Farm during two successive winter growing seasons (2011/2012 and 2012/2013) to study the effect of irrigation by saline water on soil salinity as well as investigate the possible effects of foliar application of silicon on alleviating the adverse effects of salinity and the possible mechanisms by which silicon could increase wheat tolerance to salinity. The experimental design was split plot design with four replicates, where six salinity levels of irrigation water (0.5, 4, 6, 8, 10 and 12 dS m^-1) were assigned as the main plots , while the silicon treatments (0, 1 and 2 mmol L^-1) were assigned as the sub-plots. Fresh water was used till complete germination, and then saline water was used. Results showed that irrigation by saline water up to 12 dSm^-1 greatly affected the soil EC, and the contents of soluble sodium and chloride. Significant decrease in wheat dry weight was observed with increasing salinity of irrigation water. Foliar application of silicon to wheat plants at tillering and booting stages alleviated the salinity hazards effect and resulted in increasing wheat grains and straw dry weight by about 22.5 and 21.4 %, respectively under irrigation with saline water (EC=12 dS m^-1) and 1 mmol L^-1 silicon compared to silicon absence treatment. However, 1 mmol silicon L^-1 is superior to other levels in decreasing salinity hazard on plant. N, P and K contents are decreased in wheat plant with increasing salinity of irrigation water while sodium and proline contents were increased. Foliar application of silicon resulted in increasing N, P, K and proline contents, while sodium content of wheat plants was decreased at different salinity level as compared to the control. Therefore, silicon increased salinity tolerance of wheat may be through two possible mechanisms: 1) Silicon  application either at low or high concentrations (1 or 2 mmol L^-1) led to increase K uptake and decrease Na uptake by wheat plant which adjust the osmotic pressure and encourage nutrients uptake , hence increase plant tolerance to salinity. 2) Silicon application resulted in increasing proline content in salt stressed wheat plants, which possibly acting either as buffer against osmotic imbalance due to high vacuolar ions concentration or as a protective agent for cytoplasmic enzymes.