Aiming at the problems of difficult fault diagnosis for heavy forging hydraulic press, as well as the problems of time-consuming and laborious, long troubleshooting cycle, only qualitative analysis and inaccurate fault cause diagnosis for traditional diagnosis methods, a method of state analysis and fault diagnosis for heavy forging hydraulic press based on manufacturing knowledge was proposed, and the fault diagnosis process and selection method of analysis method were given. Taking the failure of slider unable to return as an example, the test steps of fault tree and the inspection process of fault cause under the guidance of fault tree were explained. Finally, the fault tree level of heavy forging hydraulic press was divided into four levels, and the hazard of each level and the handling methods and methods were given, so as to realize the rapid identification and diagnosis analysis of faults in the remote operation and maintenance of heavy forging hydraulic press.