The viscosity of the steam turbine oil is greatly affected by temperature, if the temperature is too low, the oil film is thick and not stable, which will have adhering function on the shaft and will easily cause vibration and even vibration of oil film. However if the oil temperature is too high, its viscosity will be reduced too much, so that the oil film it too thin. Too thin oil film is also unstable and is easily damaged, therefore there is a certain requirement on the upper limit and lower limit of oil temperature. In the initial period of starting, the linear velocity of shaft neck surface is low, the specific pressure is high, the viscosity of the steam turbine oil is less, so the stable oil film cannot be established.