Abstract: In order to investigate the effect of specially-shaped packet materials on the moisture retention for cigarettes, the isothermal adsorption curves of cut tobacco, cigarette paper, tipping paper, sulfate paper, filter rod and packet materials were established post production. The correlation curves between water activity and moisture contents were fitted by the DLP model equation, and the fitting results were verified. According to the law of mass conservation and the fitting results of the DLP equation, a prediction method for the moisture content in each material used in the specially-shaped packet was constructed, and a verification test of the method was conducted. The results showed that: 1) The determination coefficients of the fitting results were all higher than 0.999 0 by using the DLP model equation, and the average relative errors of the measured and predicted moisture contents were all less than 5%, indicating that the equation was suitable for evaluating the performance of the materials. 2) Under the condition of 90% relative humidity, the specially-shaped cigarette packet with a good moisture sealing degree could better isolate the influence of the environmental humidity within 15 days. 3) The same cigarettes were packed in the packets balanced at different relative humidity, and the moisture content in the packet system could reach full equilibrium after 18 days. 4) The prediction method optimized with the law of conservation of mass and the fitting results of the DLP model equation was accurate for the moisture content in each of the material in the packet system. The packets with different moisture contents in the materials had different effects on cut tobacco, filter rod, and sulfate paper, which indicated that the moisture content in cigarettes could meet the quality requirements by controlling the moisture contents in the materials within a reasonable time range.