Abstract: With the extracts of Puerariae Lobatae Radix as the research object, the moisture absorption isotherm at 298, 308 and 318 K was determined through dynamic water vapor adsorption. Moisture absorption isotherm models were applied to the simulation of moisture absorption behavior. The enthalpy, entropy and Gibbs free energy for moisture adsorption were calculated according to the model and the enthalpy-entropy compensation was used to analysis moisture adsorption process. It was shown that the adsorption isotherm coincided with GAB model or Ferro-Fontan model. Moisture absorption process was an exothermic process which was driven by entropy. The effect of moisture on compressibility was evaluated through tensile strength and elastic recovery with water content, pressure force and speed variation. It was supposed that right amount of moisture was required to compression and compaction.