The utility model relates to a magnetorheological finishing device for an internal wall of a capillary tube, belonging to the technical field of finishing and grinding of precise devices. The magnetorheological finishing device comprises a support body, a magnetic field controller and a driving system, wherein a magnetorheological fluid injector and a vibrator are arranged on the support body. The magnetorheological finishing device solves the technical problem of injecting fluid into the capillary tube; the fluid flows smoothly in the capillary tube through the vibrator, while the magnetic field controller is controlled to lead the magnetorheological fluid to form a flexible finishing die in the capillary tube under the action of a magnetic field so as to perform efficient polishing on the internal wall of the capillary tube to lead the internal wall of the capillary tube to achieve hyperfine smoothness; therefore, the stability of applications such as analysis and test as well as the precision of corresponding test results are improved, the service life of the capillary tube is prolonged, the loss reduction is facilitated, and the cost is lowered; and the magnetorheological finishing device is suitable for efficient polishing for small devices similar to the capillary tube manufactured by non-magnetic materials, particularly for precise processing such as internal polishing for the small devices similar to the capillary tube.