Abstract: In order to explore the effects of different fertilization treatments on soil organic carbon (SOC) fractions and respiration rate under tobacco cultivation, a pot experiment was conducted to study the dynamic changes of SOC fractions and soil respiration rate during the growth stages of tobacco plants under the treatments of no fertilization (CK), single application of nitrogen (N) fertilizer, combined application of N, phosphorus (P) and potassium (K) fertilizers, and application of decomposed straw, sesame cake fertilizer and biochar. Compared with CK and single application of chemical fertilizers, the contents of SOC fractions and soil respiration rate were increased after the application of organic materials. In the treatments of organic materials application, the content of total SOC was the highest, while the cumulative CO₂ emission was the lowest after 60 days of transplanting in 2017 and 2018. The content of total SOC in the straw application treatment was second only to that in the biochar application treatment, and the cumulative emission of CO₂ was the highest. The application of organic materials increased the content of SOC fractions, and fertilization treatment improved the soil respiration rate. Compared with the other organic materials application, biochar was beneficial to the retention of SOC and the reduction of CO₂ emission.