<p>Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests. A randomized block experiment simulating warming, rainfall increase and nitrogen addition in a <i>Larix gmelinii</i> forest was carried out to study the effects on soil carbon, nitrogen, and CO₂ flux during the thawing, growing, and freezing periods. Our study found that warming (0–2.0&#xa0;°C) increased soil organic carbon (SOC) and total nitrogen (STN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN). Warming played a direct role in regulating soil CO₂ emissions, stimulated microbial and plant root respiration and soil CO₂ flux rapidly increased. Rainfall increase initially increased soil carbon and nitrogen, but a 30% increase in mean annual rainfall caused losses of SOC, STN, DOC, and DON, while MBC and MBN accumulated. Soil CO₂ emissions were regulated by MBC after an increase in rainfall, excess moisture inhibited microbial activity, and soil CO₂ flux showed a trend of R2 (20% rainfall increase) &gt; R1 (10% rainfall increase) &gt; CK (control) &gt; R3 (30% rainfall increase). The addition of nitrogen increased SOC, STN, DOC, DON, MBC and MBN. Soil CO₂ flux progressively decreased with nitrogen inputs (2.5, 5.0 and 10.0&#xa0;g&#xa0;m⁻²&#xa0;a⁻¹), as more N intensified plant–microbe competition. Nitrogen addition indirectly regulated soil CO₂ emissions by altering SOC and STN, with MBC and MBN acting as secondary regulators. The results highlight the role of cold-temperate coniferous forest soils in predicting carbon-climate feedback in high-latitude forest permafrost regions.</p>