The invention discloses a method for capturing CO2 through Cu/Ca-based compound combined cycle. The method comprises the following steps: adding carbon-based solid fuel, a calcium-based absorbent and a copper-based oxygen carrier into a fuel reactor, and reacting by taking CO2 as a fluidizing agent at the temperature of 900-950 DEG C; separating the reaction mixture, allowing one part of the reaction gas mixture to enter the fuel reactor to serve as a fluidizing agent through a circulating fan, and allowing the residual part to pass through a compressed purification device to capture CO2; allowing the reaction solid mixture to enter an air reactor, and reacting by taking air as a fluidizing agent at the temperature of 650-700 DEG C; and separating the reaction mixture, discharging the reaction gas mixture into atmosphere, and allowing the reaction solid mixture to enter the fuel reactor to continue a circular reaction. The invention also discloses a device utilizing the method. According to the method, complete CO2 capture in a carbon-based solid fuel chemical looping combustion mode is realized, the discharge amount of greenhouse gas is reduced, and in-furnace desulfurization of the fuel reactor is realized.