Based on the analysis of the mechanism of falling film evaporation and condensation, a new solar desalination unit with three effects regeneration was designed. The performance of the unit was tested through in-door experiments, using an electric heater as heat source. The results indicate that the unit has relatively high performance ratio because of a considerable fraction of the latent heat of condensation and the sensible heat of the warm condensate being successfully utilized three times to preheat and evaporate the feedstock. The unit has also excellent transient-state performance because of using the thin layer evaporation and falling film condensation which are the most effective processes for heat and mass transfer. When the operation temperature is over 90 degrees C and the inner pressure is below 15 kPa, the performance ratio of the unit can reach about 2.35 and its yield ratio can reach about 135 kg/h. The main factors influencing the performance of the unit were researched and analyzed. The reasonable ranges of some parameters were presented. (c) 2005 Elsevier Ltd. All rights reserved.