Aim Based on the properties of magnetorheological (MR) fluids which are materials having flow properties that can be modified with magnetic field, the principle and the feasibility of shock damper using the MR fluids are discussed. Methods The configurations of the MR fluids shock damper, control system, and related theories are presented. Results Computation shows that the performance of the MR fluids shock damper, the resistances to shock, has effectively improved. Conclusion To apply the MR fluids to shock damper, the performance of the shock damper can be actively controlled.