Abstract: In order to understand the mechanism of sodium silicate on enhancing the resistance of rice to sheath blight. We hydroponically cultured two rice cultivars with different resistances to Rhizoctonia solani (R. solani) infection (resistant cultivar 91SP, susceptible cultivar Lemont) and invested the impacts of sodium silicate on rice exochitinase, endochitinase and β-1, 3-glucanase activities under R. solani infection. The results showed that after being inoculated with R. solani, the rice with sodium silicate application (the Si+ rice) had lower (but not statistically significant) disease rating and disease index compared to the Si-rice plants in resistant cultivar 91SP, but the Si+ rice plants of susceptible cultivar Lemont had significantly lower rating and disease index with relative control effect of 27.42% compared to the Si-rice plants. Uninoculated with R. solani, applying sodium silicate could increase chitinase activities of 91SP, and increase or significantly increase chitinase activities of Lemont, but it had little effect on β-1,3-glucanase activities of 91SP and Lemont. After being inoculated with R. solani, chitinase activities were induced to increase firstly, and then decreased. In conclusion, applying sodium silicate could enhance the resistance of 91SP to sheath blight by increasing chitinase and β-1, 3-glucanase activities, and enhance the resistance of Lemont to sheath blight by increasing chitinase activities, but the reduction scale of chitinase activities in Lemont with sodium silicate application were lower than those of 91SP.