The spindle system is the key subsystem of CNC machine tools, it has lots of failure and has comparison of a single failure phenomenon. Therefore, failure phenomenon often cannot be used to failure diagnosis and troubleshooting. In this paper, FMECA analysis methods was used, to determine the failure mode and causes of the components of the spindle system of CNC machine tools, and further calculate the damage degree of each component. Finally, the damage degree provides the reference for equipment repair strategy.