Water free electrorheological (ER) fluid was prepared using silica supported γ (aminopropyl) triethoxysilane [NH2(CH2)3Si(OEt)3] as the dispersed particle.The effects of factors such as electric field strength ( E ),shear rate (γ· ), particle content,type of dispersion medium and small polar molecule on the rheological properties of this ER fluid were investigated.It was found that the fluid using silicone oil as the dispersion medium and contains 15%(g/ml) particle,without any activator,and at the shear rate of 8.066s-1,when E increases from 0to 1.666 kv/mm,the apparent viscosity(ηn)of the fluid increased from 0.396 Pa.sto 16.669Pa.s.The higher the γthe smaller the ηa.The ηa increases with increasing of the particle content.The ER effect of the fluid using silicone oil as the dispersion medium is better than taht of using mineral oil or paraffin oil.The ER effect can be enchanced by the addition of small polar molecule aniline.But the leakage current density of the fluid will also be increased with increasing of the aniline content.