To solve the problem of excessive vibration and torque transmitted from the engine to the body of an automobile in the start/stop mode, a flow-mode magnetorheological (MR) mount with an inertial channel was designed. With the influence of the exciting current on the viscosity of magnetorheological fluid (MRF) and the effect of liquid resistance taken into consideration, a mathematical model of the damping force of the MR mount was established. The distribution of magnetic induction intensity in the damping channel of the MR mount circuit under the action of excitation coil was analyzed by using the finite element software, and the effects of the excitation current and the structural parameters of the magnetic circuit on the restoring force and controllable force of the MR mount were analyzed as well. The performance test of the MR mount and the vehicle test in the start/stop mode were carried out. The results show that the designed MR mount has good controllability and can effectively isolate the vibration transmission of the automotive engine in the start/stop mode.