To improve the stability of waterbased fluid magnetic abrasives,the compound dispersant was prepared with sodium hexametaphosphate and polyacrylic acid(PAA) as surfactants,and nanoSiO2 as the auxiliary.Through the DOE experimental design module of Minitab software,using sedimentation rate and offstate viscosity of waterbased fluid magnetic abrasives as evaluating index,the ingredient of the compound dispersant was studied by extreme vertex design,the effects of the components of composite dispersant on sedimentation rate and offstate viscosity were studied.The results show that there is synergistic effect between sodium hexametaphosphate and PAA,nanoSiO2 plays an important role in the offstate viscosity of waterbased fluid magnetic abrasives.The stability of waterbased fluid magnetic abrasives is improved by the three kinds of additives.Comprehensive consideration of the sedimentation rate and offstate viscosity,the optimum mixing ratio of the composite dispersant was determined,and the accuracy of the predicted value was verified by experiments.