Orifice is the main ways of magnetorheological damper to produce damping. According to the actual magnetorheological dampers, the related models are established. Use commercial software Fluent to analyze the flow field of the different size of magnetorheological damper’s throttle aperture, and compared with the experimental results. The results show that the main reasons for determining the initial damping and time delay effect are the flux and jam of magnetorheological fluid. The time-delay effect is the most obvious when the throttling aperture diameter is 0.2mm, and the response speed of the magnetorheological damper to external excitation decreases significantly with the increase of frequency.