Electrorheological (ER) fluids are regarded as smart materials with potential for application in various industries because of the controllable viscosity, the reversibly and fast response. In this paper, core-shell structured Ni/Ti/Urea nanoparticles, as an ER material, were prepared by a sol-gel method. TEM, XRD and FT-IR spectra demonstrated that the Ni nanoparticles have been homogeneously coated with a 2 nm thick layer of TiO2 containing polar groups. The polar groups were caused by the introduction of urea. The ER effect of the fluids of Ni/Ti/Urea particles in silicone oil was investigated under a DC electric field. It is found that the ER fluids of the urea-doped Ni/TiO2/Urea particles have a high ER activity, which is 10 times that of the particles containing no urea. The polar groups in the particles are the intrinsic reasons for the enhancement of electrorheological effect.