A circulating fluidized bed boiler, comprising: furnace side walls (41, 42, 43, 44); a ceiling; an air distribution plate provided at a bottom of a furnace; and at least one air distribution cone provided on the air distribution plate, wherein: cone side walls (81, 82, 83, 84) which form the air distribution cone are provided with secondary air ports, the cone side walls (81, 82, 83, 84) are separated from the furnace side walls (41, 42, 43, 44), and a furnace combustion space is formed and surrounded by the ceiling, the furnace side walls (41, 42, 43, 44), the air distribution plate, and the cone side walls (81, 82, 83, 84); characterized in that: each air distribution cone extends upwards from the air distribution plate into an interior of the furnace and has a shape gradually tapered in an extending direction, and for each air distribution cone: the air distribution cone comprises two first inclined cone side walls (81, 82) arranged to oppose to each other; the two first inclined cone side walls (81, 82) are jointed or met at a top end of the air distribution cone, and an arris line formed by the two jointed or met first inclined cone side walls (81, 82) is substantially parallel to the air distribution plate; and the secondary air ports are provided in the two first inclined cone side walls (81, 82) respectively. furnace side walls (41, 42, 43, 44); a ceiling; an air distribution plate provided at a bottom of a furnace; and at least one air distribution cone provided on the air distribution plate, wherein: cone side walls (81, 82, 83, 84) which form the air distribution cone are provided with secondary air ports, the cone side walls (81, 82, 83, 84) are separated from the furnace side walls (41, 42, 43, 44), and a furnace combustion space is formed and surrounded by the ceiling, the furnace side walls (41, 42, 43, 44), the air distribution plate, and the cone side walls (81, 82, 83, 84); cone side walls (81, 82, 83, 84) which form the air distribution cone are provided with secondary air ports, the cone side walls (81, 82, 83, 84) are separated from the furnace side walls (41, 42, 43, 44), and a furnace combustion space is formed and surrounded by the ceiling, the furnace side walls (41, 42, 43, 44), the air distribution plate, and the cone side walls (81, 82, 83, 84); characterized in that: each air distribution cone extends upwards from the air distribution plate into an interior of the furnace and has a shape gradually tapered in an extending direction, and for each air distribution cone: the air distribution cone comprises two first inclined cone side walls (81, 82) arranged to oppose to each other; the two first inclined cone side walls (81, 82) are jointed or met at a top end of the air distribution cone, and an arris line formed by the two jointed or met first inclined cone side walls (81, 82) is substantially parallel to the air distribution plate; and the secondary air ports are provided in the two first inclined cone side walls (81, 82) respectively. each air distribution cone extends upwards from the air distribution plate into an interior of the furnace and has a shape gradually tapered in an extending direction, and for each air distribution cone: the air distribution cone comprises two first inclined cone side walls (81, 82) arranged to oppose to each other; the two first inclined cone side walls (81, 82) are jointed or met at a top end of the air distribution cone, and an arris line formed by the two jointed or met first inclined cone side walls (81, 82) is substantially parallel to the air distribution plate; and the secondary air ports are provided in the two first inclined cone side walls (81, 82) respectively. the air distribution cone comprises two first inclined cone side walls (81, 82) arranged to oppose to each other; the two first inclined cone side walls (81, 82) are jointed or met at a top end of the air distribution cone, and an arris line formed by the two jointed or met first inclined cone side walls (81, 82) is substantially parallel to the air distribution plate; and the secondary air ports are provided in the two first inclined cone side walls (81, 82) respectively.