It is well known that the limestone preparation system, which directly influences the desulphurization efficiency and the control of SO2 content in the flue dust, is one of the most important assistance system of CFB(circulating fluidized bed) unit. Generally the system includes twostage crusher and mechanical screening system, which doesn't run well in the actual operation. In addition, the capacity of the limestone powder needed is much more than the designed output of the system. Therefore, based on the limestone preparation system of Baima demonstration power plant, the limestone preparation system suitable for largescale CFB power units is designed.