Monodisperse polyaniline composite microspheres were prepared by coating porous polymer particles with polyaniline. In the presence of monodisperse porous polymer particles produced by two-staged swelling method, aniline was polymerized and in situ deposited onto the surface of the porous substrate. Product polyaniline composite particles were suspended in silicone oil and rheological behaviors of these suspensions under various electric fields were then investigated with regulating the properties of the composite particles such as conductivity, composition ratio and particle concentration.