The invention belongs to the field of coal graded gradient utilization, and mainly relates to a dedusting system in a powder coal pyrolysis process. In order to overcome the defects in the prior art, the invention designs and develops a powder coal pyrolysis dedusting system with a built-in circulating granular bed. By combining the characteristics of the reactor, the built-in circulating granular bed is utilized to perform dedusting treatment on pyrolysis gas; and by using the granular bed material as a filter material, the used filter material can be recycled, thereby efficiently solving the problem of dedusting of powder coal pyrolysis gas at low cost.