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Magnetorheological (MR) damper is widely used due to its excellent damping and controllability. A resettable magnetorheological damper with double-ended and double coils was installed in a heavy machinery. In order to study the mechanical performance of the damper under a specific impact, experimental and simulation methods were used for analysis. Through the one-way coupling numerical simulation method of magnetic field finite element (FE) and computational fluid dynamics (CFD), a numerical model with implicit dynamic mesh boundaries was established in ANSYS/Fluent based on six DOF module. A user-defined function (UDF) based on C language was used to define the constitutive model of MR fluid and capture the magnetic field. The model considered the non-Newtonian region overflowing on both sides of annular gap, the compressibility of liquid and the polytropic process of air spring. In addition, the CFD model was verified by a uniform quasi-static experiment. The results showed that under the condition of continuous power-on, the damper velocity after impact was dropped to zero within 80ms, but the piston was stopped at a displacement of 1.3mm during the reset process, and the power can be completely reset after being disconnected. During the impact, a number of different vortices were generated in the fluid domain, and the larger vortices appeared on the back side of the piston movement direction. The heat that caused temperature rise was mainly generated in the annular gap, and the temperature distribution in fluid domain was uneven. The research mainly provided research methods and theoretical support for MR dampers under impact.