In this study, an orthogonal experiment was designed by changing the preparation process parameters of bonded magnetic abrasives. Then, a series of magnetic abrasives with different specifications were prepared, and their morphology and composition were detected. Taking the 3D-printed AlSi10Mg plate as the processing object, the influence of the magnetic abrasive preparation process parameters on the polishing quality was revealed through the planar magnetic abrasive finishing experiment. A regression model between parameters and responses was established based on regression analysis, and the genetic algorithm optimized parameters. The results show that under the condition that SiC is 18~25 μm, the mass ratio of Fe to SiC is 4.7, the mass ratio of resin to curing agent is 2, the curing temperature is 100 °C, the material removal rate is 1.7 mg/min, and the surface roughness is reduced from the original 3.90 μm to 0.27 μm with a reduction of 93.1%.