We have performed static yield stress experiment using two-phased electrorheological fluids. The two-phased ER fluids consist of mixing different kinds of micron-particles (≅1 μm) like Barium Titanate (BaTiO3), Lead Titanate (PbTiO3) or Lead Zirconate Titanate (PZT) with 55 μm glass sphere in silicon oil. For fixed solid / liquid volume fraction, peak is observed by plotting static yield stress versus particle ratio. We have used effective medium approach, which assumes the micron-particles modifying the properties of the liquid and glass sphere, and to explain our results.