In order to further study the effects of nitrogen managements on the culm lodging of direct-seeded rice, based on the optimum seeding rate and nitrogen application method clarified in our previous study, two field experiments were conducted with hybrid rice F you 498 and the new-selected hybrid rice De you 4923 as the materials. Five nitrogen levels (90, 120, 150, 180 and 210 kg·hm-2, the ratio of basal fertilizer: tillering fertilizer: earing fertilizer was 3∶3∶4) in experiment 1; and four nitrogen application treatments based on the nitrogen level was 150 kg·hm-2 (the ratio of basal fertilizer: tillering fertilizer: earing fertilizer was 10∶0∶0, 4∶4∶2, 3∶3∶4 and 2∶2∶6, respectively) in the second experiment were set up to study the difference in culm morphology, mechanical index, chemical composition of the culm and its relationship with lodging resistance of direct-seeded rice under different nitrogen levels and nitrogen application methods. The results showed that the bending moment of the whole plant, section modulus, bending stress, culm diameter, and the carbohydrates content and K content of the fourth internode were decreased with the increasing nitrogen level or the rate of earing fertilizer. The increase of nitrogen level was accompanied by the elongation of the internodes, the increase of the plant height and the height of the gravity center, which resulted in the increase of lodging index and the higher lodging risk. Hybrid rice cultivars F you 498 and De you 4923 could have the higher grain yield and lodging resistance of culm in direct-seeded rice at 150 kg·hm-2nitrogen level combined with the ratio of basal fertilizer: tillering fertilizer: earing fertilizer was 3∶3∶4 and 4∶4∶2, respectively. Moreover, the bending moment at breaking, the outer diameter of the major axis, hemicellulose content, and N content play a vital role in the lodging resistance of culm in direct-seeded rice. This study provides a theoretical basis for the rational management of nitrogen fertilizers in the development of direct-seeded rice technology.