A special desalinization unit which utilizes solar or waste energy has been developed and tested indoors. In this unit, a relatively large fraction of latent and sensible heat of condensation along with brine is successfully recycled and utilized. It is used to preheat and evaporate the feedstock due to the multi-effect thermal regenerative process. Since the failing film evaporation is used and the system posses the characteristics of flash distillation and vapor compression, the thermal performance of the system is improved greatly. As a result of the simulation of the unit operating with a solar system under practical weather conditions, the yield is about two times greater than that of a conventional single basin solar still with the same thermal energy input. The transient-state performance of the unit, the relationships among the operating temperature, feedstock flow rate and the productivity are presented. Other factors which influence the freshwater yield are also discussed.