The work aims to improve the stability and machine ability of water-based fluid magnetic abrasives.Carbonyl iron was used as magnetic particles, green silicon carbide was used as abrasive.With static sedimentation rate and the zero viscosity index, the extreme vertex method was adopted to determine the optimal proportioning of two kinds of dispersants and nano SiO2, on the basis of the results of single factor experiment of the effect of sodium carboxymethyl cellulose (CMC) and sodium hexametaphosphate (SHMP) on the stability of water-based fluid magnetic abrasives.The dispersing mechanism was investigated, and the processing capacity was tested on the surface roughness of duralumin workpiece (YL12) .The experimental results show that when the mass fraction m (SHMP) ∶m (CMC) ∶m (nano-SiO2) =0.225∶0.055∶0.72, the comprehensive optimal value for static sedimentation rate and zero viscosity index was 3.34%and265.07 (mPa·s) , respectively.After processing, the surface roughness of the specimens decreased from 0.388 to 0.047μm.The composite dispersant SHMP and CMC was superior to the single dispersant, the stability and machine ability of water-based fluid magnetic abrasives was improved, the processing effect was good, the surface roughness of the workpiece was greatly reduced and the redispersibility was high after processing.