A mass transfer model for devolatilization process of highly viscous media in rotating packed bed (RPB) was developed based on penetration theory and mass conservation. Before establishing the model, some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study, acetone was used as the volatile organic compound (VOC) and syrup as the highly viscous media. The thickness of thin film was changed by using different liquid distributor. It was found that bubbling played an important role in the devolatilization. The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed. The relative error between predicted and experimental data was within the range of +/- 30% for diffusion coefficient of acetone in syrup. A comparison of experimental data of RPB with model indicated that the relative error was within +/- 30% for efficiency of acetone removal.