Abstract: In order to predict the isothermal absorption curve and water activity of blended tobacco,the applicabilities of Smith model and DLP model in describing the isothermal absorption curves of different type tobacco samples were investigated.Prediction models were established based on mass equilibrium equation,and the established models were validated.The results showed that DLP model fitted more precisely than did the Smith model in describing the isothermal absorption characteristics and applied to a wider range of water activity of tobacco samples of different types.The maximum mean relative error of prediction models for isothermal absorption curves of 6 tobacco samples(including cut reconstituted tobacco,cut stem,cut strips,cigarette,tobacco rod and filter sections of cigarettes) was 4.51%.The maximum,minimum and mean relative deviations of predictive values of water activities of 18 blended tobacco samples were 6.33%,0.58% and 1.90%,respectively,with the determination coefficient R² of 0.993 9.