Abstract: Diesel engine is the main power source of agricultural machinery and equipment, and the fault form in the working process is mainly abnormal wear.This paper constructs the technical means of abnormal wear fault detection of agricultural diesel engine based on infrared spectrometer, and tracks and monitors the operation process of agricultural diesel engine combined with fault monitoring and diagnosis analysis process, Judge the abnormal wear fault of diesel engine, and verify the accuracy of fault detection and diagnosis in combination with the engine disassembly and maintenance state. The results show that the fault detection and diagnosis process of diesel engine constructed by infrared spectrometer can effectively diagnose and analyze the abnormal wear state of agricultural diesel engine.