Abstract: The research about how the different amount of silicon fertilizer affects flexural strength of culm provides important cues for the rational application of fertilizer and improving lodging resistance during the growth stage of rice. In this study, three indica varieties (combinations) with different lodging resistance abilities were used as materials for conducting research on the effect of flexural strength of three basal internode and anti-thrust of whole plant under three levels of silicon fertilizer during grain-filling stage. After appling silicon fertilizer, flexural strength of internode was improved greatly compared with normal control (without silicon fertilizer). A wider range of increased flexural strength can be observed under D2 treatment. The increased flexural strength of three varieties was also varied. Of which,‘Lvyou1’and‘Shanyou63’performed best flexural strength under the treatment of 60 kg/hm² silicon fertilizer, while‘Zhongyou838’had the best flexural strength under the treatment of 30 kg/hm² silicon fertilizer. However, to some extent, the performance of anti-thrust of whole plant and the flexural strength is different. The results suggested that the anti-thrust of whole plant performed best under the treatment of 30 kg/hm² silicon fertilizer, and the anti-thrust of single culm also showed high value. Moreover, three varieties displayed consistently. In general, medium-planting indica rice varieties may be appropriate to the application of the silicon fertilizer to improve lodging resistance during the rice production. Generally, 30 kg/hm² pure silicon was applied, and the amount should not be applied too large, appropriate amount could be adjusted according to different varieties.