System configurations of water recycling for space use have been continued through theoretical and experimental studies. The water recycling system plays a central role in a Closed Ecological Life Support System (CELSS) which offers necessary environment and life styles in closed environment such as space stations, lunar bases, etc.. Membrane technology is a possible candidate for purifying waste water produced by crew use facility, plant cultivation facility, etc. In considerations of the system compactness realizing energy saving, membrane distillation has been revealed to be a suitable purification process. Ground experiments has been performed using membrane filtration processes and membrane distillation process. Thermopervaporation technology with hydrophobic membrane is utilized in the distillation process. The energy saving is achieved by thermal return of condensation energy.The candidate water recycling system can be composed of membrane distillation as a primary process, realizing a system efficiency. The degassing process is required to remove gas contained in purified water. In the μ gravity environment, absorption type thermopervaporation distillation is suitable. Under the gravity such as on the moon, the ordinary construction similar to a ground-based one can be applicable, being convenient for the gas separation.