The work aims to improve of magnetic abrasive finishing efficiency of small-diameter TC4 tubes. A flexible magnetic chain consisting of several radial magnetized poles was placed inside the workpiece, so as greatly improve magnetic induction intensity in the whole machining area. Assisted by a plurality of motions, efficient precision polishing on internal surface of small-diameter elongated tubes was completed. Law of influence of workpiece revolving speed, particle size and volume of grinding fluid on the finishing efficiency was studied in response surface methodology. When the average particle size of abrasive particles remained unchanged and the revolving speed ranged from 18 000 to 20 000 r/min, the surface roughness value tended to be stable; when the volume of grinding fluid was 8 mL, the surface roughness value reached the minimum; when the volume of grinding fluid remained unchanged and the revolving speed ranged from 18 000 to 20 000 r/min, the surface roughness value tended to be stable; when the average particle size was 250 μm, the surface roughness value reached the minimum; when the workpiece revolving speed remained unchanged, volume of grinding fluid was 8 mL and the average particle size was 250 μm, the surface roughness reached the minimum. After the 40 min grinding, the surface roughness value Ra in all positions on the workpiece fell within 0.35~0.2 μm stably. Optimized combination of process parameters is as follows: revolving speed of 20 000 r/min, volume of grinding fluid of 8 mL, and average particle size of 250 μm. The machining uniformity of inner surface is improved obviously after the workpiece is machined, original defects are completely removed and best effects are achieved.