For the phenomenon of sub-synchronous vibration of high speed rotor and hydrostatic-dynamic hybrid gas lubrication bearings system, taking into account the characteristics of shaft vibration on change of gas film pressure and cushion, an experiment on the sub-synchronous whirl and whip was carried out. It uses shafting modal analysis, to get variation curve of the system natural frequency coupled with the bearing supply pressure. It uses non-linear test analysis method, to study shaft center orbits, frequency coupling 3-D plot, and bifurcation plot of sub-synchronous vibration. The results turn out adding silica gel spacer under the basis can reduce amplitude of critical speed, put off occurrence of sub- synchronous whip.