Abstract: In view of the lack of research and related data on CNC grinders nowadays, the failure situation of 30 MSK series cylindrical CNC grinders manufactured by a machine tool factory was tracked and counted for a long time by using the method of non-replacement timing truncation test. To find out frequent failure modes, the failure data of CNC grinders were grouped according to the failure mode and subsystems respectively. It is result that the key subsystem which has the greatest impact on the reliability of the whole machine is the electronic control system (EC), while the mean time between failures (MTBF) of the system is increased by 10%, the MTBF of the whole machine would be able to increase by 2.06%. Then, in order to improve the reliability of electronic control system, FTA (Fault Tree Analysis) was used to find out the causes of frequent faults in the system. The qualitative analysis of the fault tree, via utilizing Semanderes method, obtained the 29 minimum cut sets, while the main cause of frequent faults in the system is the poor reliability of outsourced parts. By improving and optimizing, the MTBF of the whole grinding machine is improved to 1 500 hours, which verifies the effectiveness of the proposed method.