The effect of some fatty acids on the flocculation and dispersion properties of r-Fe203 particles in magnetic slurry was investigated. For preparation of the magnetic slurries in this experiments, r-Fe203 powders, some straight chained fatty acids with carbon numbers of C9-C21 in the alkyl chain and toluene-cyclohexane solution were used. The rheological properties of the slurry，namely the flow curve，yield stress and sedimentation volume of the r-Fe203 slurry were measured. It was found that the flow characteristics of the slurry varies depending on the alkyl chain length for each fatty acid added. The addition of stearic acid gives the best dispersion in our experimental trials. From the result of the calculation of the energy acting between particles，it was found that r-Fe203 particles in the slurry have a strongly magnetic attractive force
