A fluidized bed two-stage gasification and flash light calcined magnesite integration process, wherein a fuel is dried/pyrolyzed or partially gasified in a pyrolyzer; a product of the pyrolyzer is continually gasified in a gasifier, and then dust is filtered to produce a clean fuel gas; the fuel gas is burned in a burner to generate a hot flue gas to rapidly calcine magnesite; gas-solid separation is performed on the calcined product; the light calcined magnesium product subjected to a cooling treatment is delivered to a storage tank; and the flue gas subjected to a calcination treatment traverses a flue gas heat exchange system to preheat magnesite powder and air required for a reaction. The described process has a high integration degree, high thermal efficiency, a continuous and stable process, no coal gasification waste water, and high product activity and uniform quality.