The invention belongs to the field of combustors, and particularly discloses a flameless combustor without preheating and switching. A fuel feeder comprises a fuel nozzle, auxiliary air nozzles and afirst backflow cavity, wherein the fuel nozzle vertically extends into the bottom of the first backflow cavity, and the auxiliary air nozzles are symmetrically arranged at the top edge of the first backflow cavity; the first backflow cavity is provided with a first annular entrainment port, a second annular entrainment port and a fuel outlet, and is used for entraining flue gas and providing a combustion space for flameless combustion of fuel; and an air feeder comprises an air nozzle and a second backflow cavity, wherein the air nozzle vertically extends into the bottom of the second backflowcavity, the second backflow cavity is provided with a third annular entrainment port and an air outlet, so that a large-scale circulation is formed in a hearth. According to the flameless combustor without preheating and switching, a vortex backflow area can be formed in the first backflow cavity, so that the temperature distribution in the first backflow cavity is ensured to be uniform, the fuelis stable in flameless combustion under the action of the flue gas, and the temperature distribution in the whole hearth can be ensured to be uniform.