Abstract: This paper elaborates the state-of-arts of studies on some problems in rotor dynamics, which are as follows, l.some special vibration behaviours caused by the rolling bearings; 2.aero-elastic forces produced in the labyrinth seals; 3. vibrationmechanisms of the mistuned bladed disk; 4.mechanisms of the SFD; 5.vibration monitoring of the cracked shafts; 6.flutter whirling of the propeller rotor system.Some opinions of the author about these problems are stated, such as improving the model of a mistuned bladed disk may be one of the most important measures to gain the confident results of research on this subject, some aspects must be taken seriously in research of monitoring the cracked shafts,etc.