The utility model provides a fluidized bed boiler load adjusts and low -nitrogen combustion device adds the input port that a diversion pipeline connects backflow fan on the flue gas pipeline between sack cleaner and draught fan, backflow fan's output pipeline communicates to the entry of air -blower, and the output tuber pipe of air -blower communicates behind air heater to the beneath air intake of fluidized bed boiler, in the charging system that reducing equipment and one set of coal of a coal were add to furnace one side of fluidized bed boiler, the furnace who is connected to the fluidized bed boiler through screw feeder is exported to the reducing equipment of coal, and the charging system of coal also is connected to the furnace of fluidized bed boiler, there is the secondary air mouth at the furnace of fluidized bed boiler mid -mounting. The utility model discloses oxygen content table or nitrogen oxide content table and automatic control device still have. The utility model discloses the special regulation operation that can realize ultralow load to reach the environmental protection effect of low -nitrogen combustion, minimum discharge.