Abstract: To investigate the effects of biochar application on tobacco field, pot experiments were conducted to study the impacts of straw biochar at different levels on tobacco growth, soil organic carbon and enzyme activities. The results showed that the growth of tobacco was promoted by biochar application in the soil at moderate levels (0.2%-1.0%). Tobacco height, tobacco leaf area, and the biomass of stem and leaves were all increased with moderate levels but inhibited by the high level (5.0%) of biochar application. Different from the aboveground organs, the growth of tobacco roots and the root/shoot ratio were both promoted with the tested levels of biochar application, with the 5.0% level of biochar treatment having the highest root biomass and root/shoot ratio. Moreover, the contents of soil organic carbon and active organic carbon both increased with the increase of biochar application, reaching the highest values in the 5.0% biochar treatment. The increase of active organic carbon was however less than that of total organic carbon. The soil urease, invertase and acid phosphatase activities all increased in different extent with the increase of biochar application, but the catalase activities were decreased or not changed. In summary, the effects of straw biochar application on tobacco growth and soil biological activities are very important, but the interaction between biochar and soil is a long-term process in tobacco field. Long-term experimental studies should be conducted to test the positive and negative effects of biochar application on tobacco growth and development and its related mechanisms.