To solve the problem of particle agglomeration in Magnetic Compound Fluid (MCF), the anionic surfactant Sodium Dodecyl Benzene Sulfonate (SDBS) is used to improve the dispersion of MCF and the surface quality of polishing with different mass fraction of SDBS added to MCF. The particle size distribution and median particle size in the polishing solution are measured by laser particle size distribution instrument. Zeta potential distribution of polishing solution is observed by Zeta potential analyzer to verify the dispersion effect. The surface polishing of 304 stainless steel workpiece is carried out by using MCF with different SDBS content, and the influence law of SDBS content on MCF polishing material removal rate and surface roughness is investigated. When SDBS is added to 3%, the median MCF particle size decreases from 6.845 μm to 1.640 μm, the absolute value of Zeta potential increased from 13.2 mV to 53.8 mV, the removal rate of polishing material increased from 3.11 mg/min to 3.25 mg/min, the surface roughness Ra decreased from 0.27 μm to 0.09 μm, and the surface quality is significantly improved. When the SDBS mass fraction continues to increase to 5%, 7%, the dispersion effect tends to saturation and the polishing quality remains stable. SDBS with appropriate mass fraction added in MCF can effectively solve the problem of abrasive particle agglomeration, improve the dispersion of MCF, and improve the surface quality after polishing.