In view of the low level of intelligent monitoring and insufficient intelligence of CNC machine tools at present,the intelligent monitoring and fault diagnosis system for CNC machine tools based on 5G communication was proposed.The ultra-low power STM32 was used as the hardware core,and was equipped with the AliOS Things embedded operating system to realize monitoring of the working current,voltage,temperature and vibration signals of the machine tool motor real-time.Then the time-frequency domain features of the signal were extracted to realize fault status identification,and the abnormal status data were uploaded to the remote intelligent monitoring service platform by using the 5G communication intelligent gateway.Meanwhile,the platform can issue instructions to the monitoring system,prompt and assist staff to timely maintenance the CNC machine tools with fault risky,which can ensure the reliable and stable operation of CNC machine tools.After testing,the monitoring system can achieve high-concurrency and massive data collection and high-speed transmission.The 5G communication transmission speed is 500 Mb/s,the transmission delay is within 20 ms,the average data packet loss rate is within 2%.The test results show that the system has stable and reliable performance,which not only meets the intelligent monitoring of CNC machine tools,but also provides technical solutions for the intelligent upgrade of CNC machine tools.