Abstract: The spalling reason of Babbitt layer of steam turbine lower bearing of one ultra supercritical unit was analyzed by means of chemical composition analysis, X-ray diffraction, metallographic examination and so on. The results showed that the chemical composition of the Babbitt layer significantly deviated from the requirement of GB/T 1174-1992 standard and the proportion of ε and β ′ phase was exorbitant resulted in the spalling. It was suggested that the control of the quality and manufacturing process of the bearing must be emphasized.