When the diesel engine runs normally, its sound is rhythmic, uniform exhaust noise and slight noise, and has certain regularity. When the parts of the diesel engine are loose because of the loose wear or improper adjustment, the gap between the matching pairs will be destroyed and abnormal sound will appear, such as the abnormal sound of knocking, the sound of the gun and so on. When the diesel engine occurs the abnormal sound, the cause of the noise should be analyzed according to the failure phenomenon, and the location of the noise should be found so that effective measures can be taken in time to avoid the occurrence of the malignant accidents. The abnormal noise caused by damage and loosening of parts should be repaired and replaced. Abnormal noise caused by excessive clearance should be adjusted, repaired or replaced.