Abstract: The effect of silicon supply on the biomass and physiochemical features of tall fescue seedlings was investigated under different salinization conditions using a water culture experiment. Biomass decreased as salt concentration increased, with 200 mmol/L proving to be the critical concentration for tall fescue seedlings. When salt concentration was less than 200 mmol/L, silicon addition significantly increased seedling biomass, indicating that the effectiveness of silicon on tall fescue is closely related to salt concentration. If the concentration was more than 200 mmol/L, there was no significant effect of silicon addition on biomass. Under water culture, the activities of SOD, CAT and POD were increased and the contents of malondialdehyde, proline and water soluble sugars, and relative conductivity, were decreased by adding silicon to seedlings under salt stress below the critical concentration. The most significant reduction in MDA content (18.05%) was when salt concentration was 100 mmol/L. The most significant decline in proline content (23.63%) was when salt concentration was 50 mmol/L. The results indicate that the adaptability to salinization of tall fescue seedlings is improved by adding silicon and that silicon may be directly involved in the seedlings’ physiochemical processes.