Let us talk about the reliability of CNC machine tools. It is well known that the reliability of CNC machine tool is the most important indicators for users. It means NC system need use higher integrated chip, adopt large-scale hybrid integrated circuit to reduce the number of components to improve reliability. Through software of hardware functions, Lathe Machine can meet the requirements of various control functions. While also through automatically run and start diagnosis,online diagnosis,off-line diagnosis and others kinds of diagnostic program, it can realize fault diagnosis and alarm in the hardware and software. Using the alarm, it will help lathe machine to find out the fault point on time.By using fault-tolerant technology, it will be easy to achieve fault self-recovery.