The utility model discloses a fluidized bed boiler taking tobacco stems as fuel, aiming at providing a fluidized bed boiler which takes the tobacco stems as fuel, is capable of effectively preventing a material returning pipe from being blocked and is high in safety. The fluidized bed boiler comprises a combustion chamber and a wind chamber arranged at the lower part of the combustion chamber, wherein the combustion chamber is provided with a fuel pipe and the material returning pipe; the material returning pipe is connected with a material returning air pipe; a compressed air source is connected with the joint of the material returning pipe and the material returning air pipe by a pipeline; the pipeline is provided with a valve. According to the fluidized bed boiler, the material returning pipe is provided with the pipeline for connecting the compressed air source, and high-pressure air regularly enters the material returning pipe for washing by opening the valve regularly, so that the phenomenon of blockage caused by high ash content during combustion of the tobacco stems, as well as ash deposition and coking in the material returning pipe can be avoided, and the safety of tobacco stem combustion in the fluidized bed boiler can be improved.