Multi effect evaporator is an energy-saving evaporation device that realizes the cascade utilization of thermal energy. The core principle is to introduce the secondary steam generated by the evaporation of the previous effect material into the subsequent effect as a heating source. Through this series operation, the system can recover and utilize the latent heat of secondary steam multiple times, thereby significantly reducing the consumption of steam. In theory, the more efficiency there is, the higher the reuse rate of steam, and the more significant the energy-saving effect.