This paper describes two configurations of liquid desiccant dehumidifiers—internally cooled and adiabatic dehumidifiers.Based on the Navier-Stokes equation，the processes of heat and mass transfers between air and liquid desiccant were modeled in vertical parallel film laminar flow.Aqueous lithium chloride was used as liquid desiccant，and the dehumidification processes were simulated on the two types of dehumidifiers with the same dimension.The parameters changes of air and liquid desiccant along the direction of plate height were obtained.A comparison between the two dehumidifiers was made under the same operation conditions.The results showed that the temperature of liquid desiccant coming from the internally cooled dehumidifier was much lower，very close to the temperature of the cooling medium，and its outlet air humidity was 5.1 g·kg-1 less than the one of the adiabatic dehumidifier，and the outlet air temperature was 10.5℃ lower.On the other hand，the concentration of the liquid desiccant changed little.The concentration difference between inlet and outlet liquid desiccant was less than 1%.