Coated-PMMA microspheres consisting of poly (methyl methacrylate)(PMMA) core and barium titanate (BaTiO3) shell were synthesized by the modified sol-gel processing and then adopted as an electrorheological (ER) materials. The structure and morphology of coated powders were characterized by SEM and FT-IR; the shear stress of the suspensions of coated-PMMA particles and pure PMMA particles in silicone oil with a 20 vol% were investigated. The results show that the BaTiO3 coated PMMA microspheres based suspension in silicone oil exhibited typical ER behavior and stronger ER effects.