Abstract: In order to study the cause of crack faults of aircraft hydraulic conduits, the macroscopic failure analysis of component was closely connected to its failure microscopic morphology and material microstructure by using macroscopic and microscopic fracture inspection failure analysis methods. The characteristics of fracture zone morphology of aircraft hydraulic conduit were analyzed, the mechanism of fracture was found out, and the root cause of fracture was found out in combination with the manufacturing and assembly characteristics and fatigue stress of hydraulic conduit. Through theoretical analysis and experiments, an ultrasonic surface wave in-situ detection method for conduit crack faults was proposed. This method fully considered the influence of various factors such as hydraulic oil, assembly, and shielding inside the conduit. Through inspection experiments, it was verified that this method can achieve in-situ detection of flat nozzle root defects and bell mouth root defects, meeting the requirements of in-service inspection.