There is a significant difference in the operating principle between the MVR evaporator and the multi effect evaporator, that is, all the steam evaporated by the MVR evaporator is reused as a heat source. After being pressurized, the steam heats the material and condenses into water. The steam heat from the MVR evaporator is circulated for the evaporation process, while the secondary steam evaporated from the multi effect evaporator, regardless of its efficiency, always needs to be condensed through the condenser, thus requiring circulating water. From this, it can be seen that the multi effect evaporator always needs to take away the heat of the final effect secondary steam from the circulating water, thereby generating condensation and forming a vacuum. The secondary steam of the MVR evaporator is recycled and does not require external heat release, so there is no need for circulating water. Therefore, the MVR evaporator has a considerable water-saving ability.