Objective To explore the effects of light intensity during internode elongation on rice (Oryza sativa L.) lodging resistance.Method Rice plants were subjected to different light intensities in phytotrons at the 1^st (S₁), 2^nd (S₂), 3^rd (S₃) and 1^st to 3^rd (S₁₂₃) internode elongation stages. The lodging resistance of rice stem and the morphological and material mechanical traits of basal internodes were measured.Result The lodging index (LI) of rice stem significantly decreased with the increasing of light intensity. LI of medium or high light intensity treatments was 34.8%-73.9% lower than that of low light intensity treatment at the S₁₂₃ internodes elongation stage. LI was significantly positively correlated with internode length, and negatively correlated with internode diameter, culm wall thickness and internode plumpness. The S₂ stage was the most sensitive period of lodging resistance to light intensity variation. Light intensity had accumulative effects on lodging resistance. The variation coefficient of lodging index at the S₁₂₃ stage was greater than those at the S₁, S₂ and S₃ stages, and similar results were found in most morphological and material mechanical traits.Conclusion The key factors to determine the lodging resistance are internode length, culm wall thickness and internode plumpness. Light intensity can significantly change the three morphological traits of basal internodes, which further affect the material mechanical characteristics of rice stem and lodging resistance.