Abstract: An experimental desalination unit with triple effect regeneration and compact construction is put forward. Performances of the unit are measured under steady state and actual weather conditions with solar collectors. Most part of latent heat of the vapor and the sensible heat of water can be utilized several times because multi-stage falling film evaporation and condensation processes are utilized. It is shown that the performance coefficient of the unit reaches about 2.0 when the stable operation temperatures are between 70 ℃and 75 ℃ and a yield rate of 10 kg/m² of freshwater can be obtained under sunshine.