Purpose <p>Recent research indicated that biochar application can enhance soil organic carbon (SOC) by 37.7% while reducing methane (CH₄) emission by 5.2% in paddy fields. However, the mechanistic pathways through which biochar regulates greenhouse gas (GHG) emissions and the compositional dynamic of SOC pools in such systems remain inadequately understood.</p> Materials and methods <p>A pot experiment was conducted to assess the impact of rice straw-derived biochar (pyrolyzed at 500℃, 1% w/w) on GHG emissions and SOC fractions in a red paddy soil. Using a 2 × 2 factorial design, treatments included an planted and unplanted conditions with or without biochar: CK (planted control), RSB500 (planted + biochar), NCK (unplanted control), and NRSB500 (unplanted + biochar) Seasonal measurements comprised CH₄ and CO₂ fluxes, soil properties, and rice photosynthetic parameters.</p> Results and discussion <p>Compared with CK, the RSB500 treatment significantly reduced CH₄ emissions by 45% and 41% during the jointing and ripening stages, respectively. CO₂ emissions were also markedly decreased at the jointing, filling, and ripening stages by 97%, 37%, and 68%, respectively. CH₄ flux correlated positively with leaf chlorophyll content and net photosynthetic rate, but negatively with intercellular CO₂ concentration. Conversely, CO₂ flux exhibited a positive correlation with plant height, biomass, and tiller number, while showing negative correlations with soil temperature, stomatal conductance, and transpiration rate. Furthermore, RSB500 enhanced both the content and proportion of dissolved organic carbon (DOC) and particulate organic carbon (POC) while significantly reducing the proportion of mineral-associated organic carbon (MOC).</p> Conclusion <p>The application of rice straw biochar demonstrates significant potential to mitigate GHG emissions and modulated SOC dynamics in paddy soils, thereby supporting strategies designed to reduce the global warming impact of rice cultivation systems.</p>