<p>Inclined holes on superalloys have important functions in aeroengines. These inclined holes need to be polished to improve surface quality before service. This study investigates the effects of time-division bidirectional flow of abrasive water on the polishing results of inclined holes on superalloys. It reveals that there is a significant imbalance in abrasive dynamic pressure and density distribution between the obtuse and acute edges inside the inclined hole during single-directional abrasive water flow polishing (AWFP). This imbalance normally leads to a non-uniform material removal on the hole wall and consequently results in a roughness variation of 50–60%. Bidirectional AWFP can effectively overcome the drawback caused by single-directional flow. It provides that the obtuse and acute edges successively experience the high dynamic pressure and density distribution of the abrasives. This improves the finishing uniformity of the hole wall, and the surface roughness variation can be reduced to 12–16%. The hole size expansion difference between the hole entry and exit also can be reduced to 10–20%. During the increase of the fluid pressure from 2 to 5 MPa, the abrasive concentration from 0.5 to 2.0 wt% and the processing time from 30 to 120 s, the roughness of the target hole decreases rapidly at first, and then changes slowly. This is related to the fact that the recast material on the hole wall is easier to remove under abrasive impingements, and the roughness improvement has a limit related to the abrasive size.</p>