Abstract: In order to evaluate the supply capacities of carbon and nitrogen nutrients in tobacco fields by different types of straw and stalk returning, the influences of corn stalk, tobacco stalk, rice straw and rice straw biochar on the organic carbon and nitrogen mineralization and nitrification in soils of tobacco fields were studied via aerobic incubation in laboratory. The results showed that:after applying different straws and stalks at 1% by weight, the soil organic carbon mineralization rate and its cumulative mineralization were in the order of corn stalk≥ rice straw≥ tobacco stalk≥ rice straw biochar≥ the control (without stalk or straw returning). At the same applying rate, the organic carbon mineralization rate and its cumulative mineralization in soils treated with rice straw biochar were significantly lower than those with rice straw. After applying the different straws and stalks, the organic nitrogen mineralization rate and nitrification rate in soils changed in similar trends, i.e. reducing first then slowly increasing and reaching a steady state. However, the nitrification rate and mineralization rate in soils treated with different straws were negative at the early incubation stage, which might be related to soil denitrification and nitrogen immobilization by soil microorganisms. Therefore, in the process of straw returning with high carbon/nitrogen ratio, proper exogenous nitrogen was needed to slow down the immobilization for facilitating soil nutrient release. Straw transformed into biochar, then returned in fields, which had better effects on carbon accumulation and nitrogen immobilization.