According to the performance distortion of a vehicle twin-tube magnetorheological fluids (MRF) damper, a new type of non-rotary body electromagnetic piston with circulation and check valve is designed based on the traditional piston structure, and the theoretical calculation method of magnetic circuit is analyzed. According to the non-rotary body characteristics of the piston, a 1/4 three-dimensional finite element magnetic circuit simulation model is established with the ANSYS edge-based Solid117 element，and the three-dimensional static magnetic field is analyzed. The new piston of MRF damper is designed and manufactured, and the piston damping channel magnetic circuit is tested, the results show that the three-dimensional simulation, the theoretical calculations, and the experimental data are consistent, and the three-dimensional simulation and the theoretical calculations of the magnetic circuit are correct. The MRF damper is designed in accordance with the requirements of techniques of a car, and the damping characteristic is tested. The results show that the damper noise source is eliminated, and that the electromagnetic piston structure with check valve is effective.