The invention discloses a three-stage cyclone separation dust collector, which comprises an outer dust bucket, wherein the outer dust bucket is provided with an outer tangential air inlet; an inner dust bucket is arranged in the outer dust bucket; a screen barrel which corresponds to the outer tangential air inlet is arranged above the inner dust bucket; the inner dust bucket, the screen barrel and the outer dust bucket are enclosed into a first-stage cyclone cavity; a rotary barrel and a group of rotary conical barrels are sleeved in the screen barrel; an air inducing barrel is further arranged in a circle enclosed by the rotary conical barrels; the air inducting barrel is inserted into the rotary barrel; the upper end of the rotary barrel is provided with a second-stage tangential air inlet; the upper end of the rotary conical barrel is provided with a third-stage tangential air inlet; an air outlet cover covers the rotary conical barrel; the back face of the air outlet cover is provided with air outlet barrels which correspond to the rotary conical barrels; the air outlet barrels extend into the rotary conical barrels; a screen cover plate further covers the air outlet cover; the screen cover plate is filled with filter cotton. According to the three-stage cyclone separation dust collector, three-stage cyclone separation is adopted, so that dust is separated more completely, and separation and coarse dust and fine dust is realized; the first stage of a cyclone system adopts the screen barrel while the second stage adopts a single cone structure, so that the structure is simple, the cost is low, and a good effect is achieved.