The damping force of a novel magneto-rheological (MR) damper was tested on MTS system in different excitation frequencies and different currents. The MR damper has three bypass holes in the piston. Experiment results indicate that the damping force has a quasi-linear relation with excitation velocity in a much broader range. Damping force also increases with applied currents. No damping force spurt at each excitation frequency. Damping force is sensitive to excitation frequencies. These characteristics make vehicles better riding comfort. At last, damping force was calculated adopting the local head loss with Bingham model or Eyring model. Damping force calculated by Eyring model matches better with experimental data. Maximum deviation of damping force in each operating condition is less than 2.3%. And if no local head loss was adopted, the damping force by calculation deviates far from experiment data. These results indicate that the calculation is reasonable and will contribute to design and optimization of MR damper.