There are many conflicting viewpoints for friction force of MR damper. Readers may be lost in facing these conflicting viewpoints. In this study, a novel model of friction force of MR damper is proposed. This model tries to reveal the essence and help readers have a better understanding of friction force of MR damper. The model indicates that the friction force only relates to the current applied to the piston coil. The friction force will increase along with current applied to the piston coil. Friction force tests for a MR damper featuring bypass holes in piston were made on a MTS852 system. The model was improved to be correct by the experiment. Friction forces by calculation with the model and by experiment are in good agreement. It is believed that sliding friction and MR phenomenon contribute to the friction force.