The invention belongs to the field of flue gas treatment, in particular relates to a sharing and resource utilization system and method of high-calcium fly ash for a multi-unit plant. Each unit of the system comprises a circulating fluidized bed boiler, a front-mounted dust remover, a circulating fluidized bed dry process desulfurization absorbing tower, a rear-mounted dust remover and an induced draft fan, wherein all units share one set of high-calcium fly ash distribution system; the high-calcium fly ash distribution system can feed fly ash collected by the front-mounted dust removers into the circulating fluidized bed dry process desulfurization absorbing towers or externally discharge the fly ash according to the content of calcium oxide of the fly ash. According to the system, the high-calcium fly ash is used as a desulfurizing agent used in a circulating fluidized bed dry process desulfurization process, and the amount of the high-calcium fly ash which is introduced into the circulating fluidized bed dry process desulfurization absorbing towers of a plurality of power generator units and the amount of low-calcium fly ash which is externally discharged to a fly ash storehouse are selected and controlled by utilizing the high-calcium fly ash distribution system according to desulfurization requirements of the plurality of power generator units and the content of the calcium oxide of the fly ash, so that on-site high-efficient resource utilization of the high-calcium fly ash is realized.