Indoor air humidity has a significant impact on indoor air quality, building energy consumption, and equipment performance. Excessively low or high humidity is not good for living and working. Hygroscopic materials can be used to moderate the indoor air humidity level. This paper presents a simplified dynamic moisture transfer model of building wall layer of hygroscopic material, and the parameter identification of the simplified model with genetic algorithm by comparing the frequency characteristics of the simplified model with the theoretic frequency characteristics. The proposed simplified model was validated against the published experimental measurements on the system level. The results show that the predicted moisture flux by the simplified model agrees well with the experimental test. The simplified model was also validated on room level by a common exercise in IEA 41 project. The results show that the simplified model has a good agreement with the analytical solution, within +/- 2.2% in the case CE1A. In the realistic case CE1B, the model prediction matches the results of these detailed models provided in public literature. The proposed simplified dynamic moisture transfer model can be used in building indoor humidity environment and energy consumption simulation with good accuracy and efficiency. (C) 2019 Elsevier Ltd. All rights reserved.