Support liquid membranes have been used in air dehumidification due to their inherent high mass transfer rates. In this study, the effects of membrane structural parameters on vapor permeation through a LiCl solution based supported liquid membrane are investigated. To aid in the analysis, a mass transfer model has been proposed for moisture transfer through the membrane, which is composed of a supported liquid layer sandwiched by two hydrophobic protective layers. The model takes into account of the resistance in boundary layers, in the protective hydrophobic layers, and in the supported liquid layer. It is a transient model. It also reflects the distributed nature of moisture permeation through the membrane. The results found that the emission rate exhibits a non-uniform distribution nature on the membrane surface. The structural parameters of the support and the protective layers, such as thickness, pore diameters, and porosity, have great effects on vapor permeation.