Magnetorheological finishing method has broad application prospects in the fields of ultra-precision processing of aspherical optical lenses. A magnetorheological test kit for the HR20 rheometer and a matching test method were designed and optimized in this paper, and the best constitutive model was found through experimental testing and curve fitting. A wheel-type magnetorheological polishing flow field model was established, and the influence of magnetic field intensity on the viscosity of magnetorheological polishing fluid, the morphology of polishing ribbon and the pressure distribution in the polishing area were analyzed. Test results of magnetorheological polishing fluids show that the viscosity and non-Newtonian characteristics of the polishing fluid increase significantly with the increase of the external magnetic field intensity. The simulation results show that the polished ribbon converges under the influence of the magnetic field, and the effective contact area with the workpiece increases. The "D" shaped pressure distribution generated on the surface of the workpiece is significantly enhanced as the external magnetic field increases.