The invention provides a reverse evaporating and concentrating system for molasses alcohol waste liquid. The flowing direction of a material is as follows in sequence: a V-effect evaporator, a IV-effect evaporator, a III-effect evaporator, a II-effect evaporator and a I-effect evaporator; low-concentration alcohol waste liquid at about 80 DEG C from a distillery enters the V-effect evaporator, and is pumped into the IV-effect evaporator and the III-effect evaporator in sequence; after medium-concentration alcohol waste liquid from the III-effect evaporator is heated to 95 DEG C or above through a first heater, the medium-concentration alcohol waste liquid precipitates and is clarified in a clarifying pond, then is heated to 105 DEG C through a second heater and a third heater, enters the I-effect evaporator, and then enters the II-effect evaporator. According to the reverse evaporating and concentrating system for the molasses alcohol waste liquid, the using amount of primary steam in alcohol production is reduced by utilizing an energy-saving transformation technical method of using secondary steam generated by multiple-effect evaporation of the waste liquid in alcohol distillation, so that the energy consumption of the alcohol production is reduced, and the production operation cost is reduced.