Magnetorheological micro jet polishing (MMJP) technology has great potential for polishing components with complex surfaces, cavities, and microstructures. However, there is a lack of in-depth and systematic research on the material removal characteristics of MMJP under different processing parameters, which hinders its engineering application. This study developed a numerical model for MMJP using the Volume of Fluid (VOF) multiphase flow model and the K-W turbulence model, which was used to analyze the interaction between the flow field and the workpiece during the polishing process. To clarify the material removal process, the material removal mechanism of MMJP was investigated. The forces acting on individual abrasives in the flow field were analyzed, and a material removal model for MMJP was established based on the Preston equation. Additionally, a combined approach of simulation and experimentation was used to study the effects of different processing parameters on material removal and polishing performance. The experimental results were consistent with the numerical predictions, demonstrating the reliability of the CFD model. Finally, an orthogonal optimization experiment was designed to determine the influence hierarchy of various process factors on the polishing results. Using the optimal process parameter combination, aluminum alloy workpieces were polished, with the surface roughness reduced from 355 nm to 253 nm. This study provides theoretical support and processing guidance for the industrial application of MMJP.