The invention provides a continuous water washing and dechlorination device for waste incineration fly ash. The device includes a dechlorination device unit, and the device unit includes a main body, a sleeve, a mixing zone partition, a water outlet weir, an agitator, a fly ash feeding pipe, a cleaning Liquid inlet pipe, mortar riser pipe, the device includes vertical flow grey water precipitation area, grey water rising area, grey water mixing dechlorination area and mortar concentration area from top to bottom, which realizes continuous fly ash cleaning in one cleaning device , Fly ash and ash water separation and transportation of mortar and waste water. The device provided by the invention can be used alone or in series. When used in series, the cleaning water flows from the cleaning device with the highest elevation of the outlet weir to the cleaning device with the lowest elevation of the outlet weir in turn, and the fly ash is sequentially lifted from the cleaning device with the lowest elevation of the outlet weir to the water. The cleaning device with the highest weir elevation. The cleaning device of the invention realizes the continuous and high-efficiency water washing of the fly ash, can be used alone or in series, and has simple and convenient operation and regulation.