Decomposition rates and nutrient release patterns of tobacco straws were studied by nylon-bag experiment. Results showed that the decomposition rate of tobacco straw were fast at the beginning and then slowly decreased with the decomposing process. During the experiment (120 d), the cumulative decomposed rates of tobacco straw were 56%, 53% and 49% for the conventional method, dolomite powder and lime treatment, respectively. The release rates of the nutrients in tobacco straw followed an order of K>P>N in all of the treatments. Within 15 d of the treatment, the release rates of K and P were about 88% and 76%, respectively, however, only about 53% of N was released from tobacco straw. Tobacco straw returning had a significant effect on soil pH. Soil pH values with dolomite powder and lime treatment were significant higher than that of the conventional treatment. Tobacco straw returning significantly increased soil available K content by 47% compared with non-straw returning treatment. Based on the above results, K in tobacco straw was inferred as water extractable and available K, thus, it should be subtracted from the recommended fertilization rate for the rotate rice.