This paper presents numerical investigations of one kind of liquid desiccant dehumidifier. A novel simulation programme is developed to evaluate the effective dehumidifier for various environments. The simulation program is built up based on a numerical model which is validated by experimental results. The results of the simulations indicate that the absorption capacity of the dehumidifier is largely influenced by desiccant mass, and less influenced by channel height, channel length, desiccant temperature, and desiccant flow rate. Although the cooling load takes inferiority roles, it is impacted by the factors in the following order: desiccant flow rate, channel height, desiccant mass concentration, desiccant temperature, and channel length. It is recommend that the efficiency absorption concentration for LiCl, LiBr and CaCl2 are 30%, 50% and 55% respectively; height and length of channel should be 10~15mm and 0.2~0.3m; desiccant temperature should be lower than 25°C; desiccant flow rate should be no slow than 3L/s. Finally, testing results proved the numerical simulation validity in acceptable error, and the factors are illuminated.