Dynamic response is a key parameter for the engineering applications of MR damper. However, the response time has many different definitions, and which leads to a confusion of the measurement. Commonly, the response of MR damper in the new-designed status is focused, the instance after long-time use or standing-still has not been proposed. In this paper, the influence on the response time by the long-time standing-still is investigated, which shows that the response is largely lengthened. Next step, the measurement will be optimized, and the response of MR damper after long-time use will be in consideration.