The influence of the machining gap on the surface integrity of the 904L high-performance stainless steel workpiece was analyzed by carrying out magnetic abrasive finishing experiment. The magnetic induction intensity of different machining gaps is compared and analyzed by simulation and testing. Under different machining gaps, the new CBN/Fe-based spherical magnetic abrasive particles prepared by the atomization method is used to finish 904L high-performance stainless steel. Use a hand-held roughness meter and a precision electronic balance to measure and analyze the surface roughness and material removal of the workpiece under different gaps. A metallographic microscope is used to observe the different changes in the surface morphology of the workpiece under different processing gaps. A stress tester is used to detect residual stress of different gaps. The wetting angle measuring instrument is used to observe and analyze the hydrophilic and hydrophobic effects of the surface of the workpiece under different gaps. When the machining gap is 2.5 mm, CBN/Fe-based spherical magnetic abrasive magnetic finishing is the best for 904L stainless steel. The surface roughness of the workpiece is reduced from 0.5 μm before grinding to 0.05 μm, and the material removal amount can reach 36 mg within 5 minutes. The surface of the workpiece is uniform, without scratches and pits. When the residual compressive stress on the surface of the workpiece increased from 127.8 MPa to 318 MPa, and the wetting angle between the surface of the workpiece and the droplet increased from 20° to 83°, and the hydrophobic effect is the best.The machining gap has a great influence on the surface integrity of 904L stainless steel processed by CBN magnetic abrasive magnetic finishing. When the machining gap is 2.5 mm, the surface roughness of the workpiece is the lowest, the surface morphology is uniform, the residual compressive stress becomes larger, and the workpiece is fatigued. The strength is enhanced, and the hydrophobicity of the surface of the workpiece becomes better, achieving the best grinding effect.