The invention discloses a DDC (Desulfurization-Dedusting-Cleansing) process and device for flue gas multi-pollutant ultra-low ammonia emission. Flue gas is sequentially treated in the following steps to be changed into purified flue gas and then discharged: on a concentration section, spraying the flue gas by an ammonium sulfate solution so as to produce mist and concentrated solution; on an absorber section, spraying mist by an ammonium sulfite solution, absorbing SO2 in the mist, and producing desulfurized mist and absorption liquid; on a purifying, dedusting and demisting section, washing and electrically decontaminating the desulfurized mist, and producing purified flue gas and scrubbing solution. According to the flowing direction of the flue gas, a core tower of the device is divided into three function areas which are isolated from one another by virtue of tower plates, and the different function areas are mutually communicated through cyclone demisting riser caps on the tower plates. The three function areas respectively form three independent circulation loops with an external tank through pumps and pipelines. The device is scientific in design, compact in arrangement and high in desulfurization and dedusting efficiency, and formation of aerosol and a tailing drop phenomenon of the flue gas can be eliminated. The process and the device disclosed by the invention can realize long-term stable operation, realize ultra-low emission and have excellent practicality and wide applicability.