Abstract: Described here in the article are the causes for the network fault of the Profibus.And also elaborated are the details about analyzing the operation of the system-equipped software STEP7 and the diagnosing repeater to identify the Profibus network fault point.Taking a certain large-sized MPM plant as an example,identification and meanings of the network fault codes,and the countermeasures for the fault are described.Meanwhile the typical fault curve is analyzed.Using the high efficient intelligent network diagnostic technology and relevant measures is capable of tremendously saving the fault-handling time to enhance the productivity.Moreover network monitoring and diagnosis with the hardware are helpful for analyzing the equipment operation status and identifying the reasons for the equipment fault.