Abstract: To investigate the unstable vibration in synchronous whirl, a rotor test rig was established. The influence of rotary speed, whirl amplitude and static eccentricity on the temperature distribution of journal cross section in sliding bearing was experimentally studied, and a heat balance model was applied for the calculation and analysis. Results show that the difference of viscous shear stress between the thinnest and thickest parts of the oil film under journal whirl leads to temperature difference on journal cross section and rotor thermal deformation. The maximum temperature difference of journal surface increases approximately linearly with rotary speed and non-linearly with whirl amplitude. With increasing of static eccentricity, the temperature difference and oil film stiffness of the journal cross section both increase. And the effect of vibration suppression caused by the increasing of oil film stiffness is greater than that caused by the thermal deformation induced by temperature difference, which decreases the vibration.