Abstract: Understanding the effects of nitrogen (N) fertilizer and diatomite application on methane (CH₄) emissions and the temperature sensitivity (Q₁₀) of CH₄ emissions of the ratooning rice system is crucial for optimizing greenhouse gas emissions from paddy ecosystem. In this study, a two-year field experiment was conducted from 2022 to 2023 in Jingzhou City, Hubei Province. Three treatments were established at the study site of the ratooning rice: no nitrogen fertilizer application (CK), nitrogen fertilizer application (N), and combined application of nitrogen fertilizer with diatomite (N+Si). The CH₄ fluxes were measured using a closed-chamber method, and the rice yields and soil properties were also observed. The results showed that, compared with the CK treatment, both the N and N+Si treatments significantly increased the rice yields during the main and ratoon seasons (P<0.05). Moreover, the rice yield in the main season was 3.75%−3.85% (P<0.05) higher under N+Si treatment than that under N treatment. The cumulative CH₄ emissions of the entire growth period (the main and ratoon seasons) under both N and N+Si treatments were significantly higher than that under CK treatment (P<0.05). However, in 2022 and 2023, the N+Si treatment significantly reduced the cumulative CH₄ emissions by 25.99%−38.66% (P<0.05) in the entire growth season relative to that under N treatment. Consequently, the N+Si treatment had significantly reduced the CH₄ emissions per unit yield in both the main by 26.52%−43.51% (P<0.05). In ratoon seasons, CH₄ emissions per unit yield under N+Si treatment decreased by 18.65% in 2022 and 41.14% (P<0.05) in 2023, respectively, compared with N treatment. Correlation analysis revealed that the influences of soil properties on the CH₄ emission flux were quite different among the various treatments and rice growing seasons. The CH₄ emission flux significantly decreased with the soil redox potential (P<0.05) in the main season. However, in the ratoon season, the CH₄ emission flux significantly increased with soil temperature and soil NH₄⁺-N (P<0.05). The CH₄ emission flux was also significantly positively influenced by the soil temperature during continuous flooding period in the main season. The N+Si treatment had the highest soil temperature sensitivity of CH₄ emission (Q₁₀ = 8.86), indicating that the addition of diatomite rendered CH₄ emission flux more sensitive to temperature changes. In conclusion, the combined application of N fertilizer and diatomite not only increases the rice yield of ratoon system but also effectively reduces CH₄ emissions from the ratooning system, making it a sustainable fertilizer management strategy.