Abstract: If the design of squeeze film damper is not properly,it will be causing the failure of its functions. There are two cases of failure of the elastic support-squeeze film damper:one is the bistable character being take place,the other is unable to stride over the critical state,i.e.,the amplitude of the rotor system has been increasing with the rotating speed increasing. Two diagrams of judging the failures have been established. One is the bistable region diagram. Provided the data of the bearing parameter cooperated with the unbalance ratio do not be selected in that region,the bistable character will not be arising. The other is the failure boundaries diagram of attenuating vibration. Provided the above-mentioned data do not be selected at the side of failure boundaries,that will not be causing the phenomenon of unable to stride over the critical state. The result of experiment proves that the above conclusions are correct. This is observed from both positive and negative respect. By experiment, the excellent functions of attenuating vibration of squeeze film damper have also been affirmed still further.