The invention relates to an anti-blockage mechanism of a threshed grain pipeline conveying system, belonging to agricultural machinery. A left driving shaft, a middle driving shaft and a right driving shaft which are connected by universal joints and provided with first comb-shaped fingers are arranged on a variable cross-section contracted pipeline, corresponding grid gaps on the first comb-shaped fingers and the variable cross-section contracted pipeline are crossed, overlapped and matched, a semi-cylindrical hood is arranged at the outer side of the variable cross-section contracted pipeline to wholly seal and encapsulate the first comb-shaped fingers, the upper side of the bending part of a constant cross-section ramping pipeline is in an open structure and provided with a cylinder with second comb-shaped fingers, and the cylinder is sealed and contained by an arc hood. The mechanism adopts a material-conveying mode of combining labor and machinery and has the advantages of high conveying efficiency, good anti-blockage effect and strong material suitability.