Abstract: The aniline-strontium titanyl oxalate (aniline-SrTi(C₂O₄)₂) particles were prepared by a precipitation method. FTIR patterns show that aniline has been added to the surface of the SrTi(C₂O₄)₂ particles. XRD patterns indicate that the particles are amorphous structure with a little of crystallization. The morphology of the particles was observed by SEM, the results of which indicate that with the increase of the molar ratio of aniline toTi atoms, n_aniline/n_Ti, the smorphology of aniline-SrTi(C₂O₄)₂ particles change from approximate globular (n_aniline/n_Ti =0) to a polyhedron shape (n_aniline/n_Ti =2), and then a mixure consists of rod and cluster shaped particles (n_aniline/n_Ti =3). The electrorheological (ER) fluids were prepared with 66.7% mass fraction of aniline-SrTi(C₂O₄)₂ particles with different aniline contentand tested. The experimental results indicate that the ER fluid prepared by the particles with a molar ratio of n_aniline/n_Ti =2 present the largest field-induced shear stress, yield stress and leak current density. The aniline controls the particle morphology during the preparation of the particles, and acts as polar molecules in the ER fluids system. The influence of the aniline on properties of the ER fluids is a combined effect of the two roles.