As the main major equipment in the power plant, the steam turbine has a complex structure and poor operating environment. Its reliability is very important for the power plant. Intelligent fault diagnosis of steam turbines is an important part of the construction of smart power plants. As a complex system, the operation state of a steam turbine may be affected by a variety of faults. Different faults are interconnected and excited each other, which is often caused by the concurrence of other faults due to the occurrence of one fault. The external phenomenon produced is the result of the comprehensive action of many factors. The intelligent fault diagnosis system of steam turbines is based on traditional parameter monitoring and further analyzes on the basis of monitoring to find out the cause of the fault and gives maintenance suggestions. It includes diagnosing the faults that have occurred to prevent further deterioration and predicting the faults that have not occurred to prevent the occurrence of faults so as to achieve the purpose of fault diagnosis, pre-diagnosis, and intelligent maintenance.