Abstract: The transient characteristics of a flexible rotor supported on nonlinear squeeze film dampers (SFD′s) during passing through the resonant and bistable operation speed range with constant acceleration are studied theoretically and experimentally.It is shown that the properly designed SFD′s have not only excellent steady state performance,but also better acceleration performance.The maximum vibration amplitude of the rotor system in the acceleration process decreases gradually with increase of rotor angular acceleration,whether for the properly designed SFD′s or for the improperly designed SFD′s.The stability of multisolution in the bistable operation speed ranges depends not only on the form of bistable operation,but also on the moving process.It is impossible for the rotor system to pass through the bistable operation speed ranges with smaller amplitudes only by means of accelerating the rotor system.