With the growing energy crisis, there is an increasing focus on renewable energy sources. Liquid desiccant dehumidification is a technology that requires less energy, and the desiccant can be regenerated using renewable energy sources. Compared to other numerical research methods, the CFD technique can provide information on the state of heat and mass transfer, as well as the flow of the solution inside the dehumidifier. Therefore, a two-dimensional internally-cooled tube falling film dehumidifier model was developed based on CFD technique in this study and validated by comparison with data from previous studies. During the transient analysis, it was observed that the solution maintained a constant speed when flowing along the tube wall. After flowing downward for approximately 16 s, it reached the bottom of the dehumidifier tube, resulting in a dehumidification rate of 96.1% compared to the stable dehumidification case. In the steady-state study, it was found that air inlet temperature and solution flow rate had little effect on the dehumidification effect of the dehumidifier under baseline conditions. An increase of 10°C in the air inlet temperature resulted in only a 6.5% decrease in absolute moisture removal (AMR), while a 33.3% increase in solution flow rate resulted in only a 3.2% increase in AMR. The dehumidification performance of solution isothermal dehumidification is 32 % higher than that of adiabatic dehumidification. The results of this study will provide a reference for the practical application of internally-cooled tube falling film dehumidifier.