The utility model relates to a low -nitrogen combustion's circulating fluidized bed boiler, its combustion system include furnace, from the bottom up was equipped with in proper order in the furnace air distribute device, burner and water -cooling wall chamber, furnace top be equipped with with the first part case that the drum is connected, the furnace antetheca outside be equipped with with the next part case that the drum is connected, two cold water screens have been add to the water -cooling wall intracavity, two water cold shield's upper and lower both ends are passed respectively furnace top and furnace antetheca, and respectively with first part case with the next part case corresponds to be connected. The beneficial effects of the utility model are that: effectively reduce combustion system's bed temperature and oxygen volume, and then reduce NO2's original emission, make fuel obtain fully, reduce fly ash combustible, improve the economic nature of boiler.