Abstract: Taking carboxyl iron powders and silicon oil as magnetic particles and carrier fluid separately,adding silane coupling agent and nano-SiO2,magneto-rheological fluid was prepared by the method of using ball mill to disperse.Through utilizing NXS-11D rotational viscometer,natural sedimentation method and MRTS-01 magnetic rheometer to test viscosity,sedimentation stability and rheological properties of the magneto-rheological fluid.The results show that zero-field viscosity of the magneto-rheological fluid was low which was 0.675 Pa·s.It decreased with the increasing of shear rate and showed shear-thinning phenomenon,which manifested the magneto-rheological fluid belonged to weak Bingham fluid.The fluid had good sedimentation stability,whose sedimentation rate for 3 months was 13% and no harden phenomenon appeared.It was quite easy to re-disperse after mixing,that presented as soft sedimentation.The shear stress could reach 60 kPa when the magnetic field intensity was 0.6 T.