Multi-effect evaporation is a heat transfer process, which is the evaporation operation of multiple evaporators in series. It is the series evaporation of the secondary steam before the effect as the next effect of heating steam, so that the steam heat can be used for many times, so as to improve the utilization rate of heat energy. Multi-effect evaporation is mostly used for the treatment of aqueous solutions, which is the process of boiling and condensation heat transfer. In multi-effect evaporation, the operating pressure of each effect, the corresponding heating steam temperature and the boiling point of the solution are reduced at a time.