The invention provides a sewage disposal fault diagnosis method and device. The method comprises that at least one piece of fault information related to sewage disposal is received; and the at least one piece of fault information is sent to an expert module, and a fault diagnosis result corresponding to each fault information is received from the expert module; or, on the basis of each fault information, a sewage disposal knowledge base, which is established on the basis of one semantic tree corresponding to a technical flow of sewage disposal, is called to determine a fault diagnosis result corresponding to the fault information. According to the sewage disposal fault diagnosis method and device, the fault information can be described accurately, knowledge in the sewage disposal knowledgebase is updated dynamically, online interaction and communication with technical experts are realized, and thus, the proper and effective fault diagnosis result can be obtained.