The quality of the internal surface plays a crucial role in the performance of parts with complex structures, which are widely used in aerospace, biomedical, chemical industries, and other fields. However, due to poor accessibility, the uniformity of the internal surface of complex internal channels is low after finishing with existing methods. In view of the poor overall uniformity of the surface processing quality of the inner wall of complex internal channel, a controllable ball blockage abrasive flow polishing method is proposed with controllable intensity to change the local polishing intensity to achieve controllable polishing of the specified area through the placement of ball blockage via traction rope. Through the design of comparative tests and numerical simulation of flow field simulation to study the effect of ball blockage machining on the processing effect and the change of flow field data to analyze the mechanism of processing intensity. The results found that: under the same processing time and working pressure, with the ball blockage, the velocity of the flow field decreases sharply, the polishing efficiency decreases gradually, and the surface quality of the ball blockage machining area is better than that of the non-ball blockage machining area; the ball blockage affects the velocity of the fluid by changing the flow area, and then controls the polishing intensity to achieve the machining effect is controllable. The ball blockage diameter is 3.75 mm, and the surface roughness of the ball blockage processing area is reduced from 1054 nm to 66 nm after 30 min of processing. The placement of the ball blockage enables the control of the machining intensity in a local area, proving the feasibility of the controllable ball blockage abrasive flow polishing method.