A test methodology for rheological behaviors of MR greases based on double rotational coaxial cylinder shear mode is presented in this paper. Both flow velocity profiles and shear stress profiles of MR greases in shear channels are analytically explored. The theory relationship between shear stress acted on MR greases and transmission torques is established, an approximate algorithm is put forwarded to acquire nominal shear stresses by transmission torques. On the basis of differential equation and its rational boundary conditions from stress equilibrium of MR greases micro-unit, an approximate corresponding algorithm is worked out for nominal shear strain rates by rotor angular velocities. The relationship between average value of magnetic flux density in annular channels and excitation electrical currents are experimentally obtained. Based on test methodology above-mentioned, a rheometer is fabricated and modulated, in which torque sensor, angular velocity sensor and ampere meter are respectively used to test transmission torque, angular velocity and electrical current. Rheological parameters of MR grease from the rheometer, whose shear rate is more than 2000 1/s and magnetic flux density acting on MR greases exceed 0.6T, are in good agreement with those from test conduced by commercial theological rheometer.