The invention discloses a circulating fluidized bed combusting desulfurization ash recycling method and a system thereof and relates to recycling of desulfurization ash produced during combustion of solid fuel of a circulating fluidized bed. The system comprises a combustion chamber, a reducing chamber, a regeneration chamber, a first gas-liquid separator, a second gas-liquid separator, a third gas-liquid separator, a first material return device, a second material return device, a third material return device and a gas combustion chamber. According to the method, desulfurization ash produced during combusting desulfurization of the circulating fluidized bed is reduced to produce CaO, CaS and SO2, and then CaS is oxidized and calcined to obtain CaO and SO2. The regenerated CaO can be circularly used for combusting desulfurization of the fluidized bed, and the separated SO2 can be used for a sulfuric acid processing technique. The system and the method disclosed by the invention are favorable for treatment of desulfurization products, can improve the overall economic benefit and is favorable for realizing large-scale circulating fluidized beds.