Membrane heat pumps are emerging as an excellent alternative to conventional vapor compression heat pumps. Because it does not use compressor which is energy consuming device, power consumption of air-conditioning equipment can be drastically reduced, and water is used as working fluid, so there is no environmental impact. In this study, the performance of membrane for dehumidification was investigated under various operating conditions for the design of membrane dehumidification module, which is a core element of membrane heat pump.