[Aim]  To explore the effects of applying silicon to rice plants on the leaf folding damage caused by Cnaphalocrocis medinalis larvae, and on rice yield. [Methods]  A 2×2 factorial plot experiment was conducted using the rice varieties Taichung Native 1 (TN1) and Zhongzheyou 8 (ZY8) and silicon application levels of 0, 150, 300, and 600 kg SiO₂/hm². The leaf folding and other damage caused by C. medinalis larvae during the tillering and booting stages, flag leaf traits at the booting stage, and rice-yield related parameters, were measured. [Results]  No significant differences in soil silicon content was observed between the rice varieties (P=0.910). However, application of 300 and 600 kg SiO₂/hm² significantly increased soil silicon content by 133.4% and 182.4% (P≤0.030), respectively in TN1 plots, and by 154.9% and 303.8% (P≤0.005), respectively, in ZY8 plots, relative to the control. At the tillering stage, significant differences were observed in the leaf position and leaf surface of the leaf-folds between different silicon treatment groups (P<0.001), with silicon application notably increasing the frequency of leaf folding on the adaxial leaf surface (P<0.001) and the number of binds per fold (P=0.020). More leaf folding was found on the adaxial leaf surface of ZY8 than TN1 plants. However, neither silicon treatment nor rice variety significantly affected the feeding rate or pupal weight of C. medinalis (P≥0.120). At the booting stage, no significant differences were found in leaf-folding characteristics, but the highest silicon treatment level (600 kg SiO₂/hm²) significantly reduced larval feeding rates (P<0.001) and increased the number of binds per fold (P=0.002). Silicon application influenced the physicochemical traits of flag leaves during the booting stage, significantly reducing specific leaf area whereas increasing chlorophyll and silicon content (P≤0.002). Yield traits were positively correlated with silicon application; silicon application significantly enhanced the number of grains per panicle, the grain-filling percentage, and the theoretical yield of ZY8 (P≤0.016). Theoretical revenue was highest at application rates of 150 kg SiO₂/hm². [Conclusion]  Silicon improves the physicochemical properties of rice leaves, enhancing leaf toughness and photosynthesis. It strengthens rice resistance and tolerance to leaf folding and other damage caused by C. medinalis larvae and increases the theoretical rice yield. A theoretical revenue analysis suggests that 150 kg SiO₂/hm² is the optimum dosage.