The invention discloses a catalysis-free reduction method two-stage denitration device of a circulating fluidized bed boiler, which belongs to the technical field of denitration of coal fired boilers. The two-stage denitration device adopts a denitration agent supply pump, a control valve and a metering system which are connected with denitration agent nozzles, and when the circulating fluidized bed boiler operates with low load, a layer or multiple layers of first denitration agent nozzles are arranged in a region (namely a lean-phase region) the flue gas temperature of which is not lower than 850 DEG C, and the top of a cyclone separator is provided with a group or multiple groups of second denitration agent nozzles. An automatic control device controls the spraying time and quantity of denitration agents from the first denitration agent nozzles and the second denitration agent nozzles through the denitration agent supply pump and the metering system. Two stages of the two-stage denitration device provided by the invention are automatically controlled to be switched on and off respectively according to the operation load of the circulating fluidized bed boiler and the flue-gas temperature variation in the cyclone separator, the smoke nitrogen oxide emission standard is met, and meanwhile, the denitration operating cost is reduced as far as possible.