Abstract: Common characteristics of magnetorheological fluids(MRF) prepared by iron grain were investigated.It explored effect of iron's particulate size,the shape,the percent of iron' s particulate and temperature on MRF characteristics.Relationship between MRF's yield stress and magnetic flux density,the shear stress and magnetic flux density and shear stress and shear rate were investigated.Magnetic saturation phenomena occured in MRF is correlated with material characteristics and percent proportion.And shear stress is correlative to iron's particulate size and preparation process.