The invention discloses a waste water reduction treatment device and method, which belongs to the field of incineration disposal of hazardous waste. The waste water reduction treatment device is usedfor matching with a flue gas treatment device to reduce the amount of the waste water discharged in the process of flue gas decontamination treatment. The flue gas treatment device includes a quench tower, a dry deacidification tower, a dedusting tower, a cooling tower and a washing tower, all of which are connected in order. The waste water reduction treatment device includes a clarification pool, a reaction tank, a cooling pool and a washing pool, all of which are connected in order; wherein the clarification pool is connected with the quench tower and the cooling tower, the reaction tank isconnected with the dry deacidification tower, the cooling pool is connected with the cooling tower, and the washing pool is connected with the washing tower. By utilizing the waste water reduction treatment device, the amount of the waste water discharged of the current system can be greatly reduced.