Metal tubings，owing to their structural characteristics and complex service environments，were prone to leakage failures，significantly compromising their reliability.Based on multiple typical failure cases，this study systematically analyzed the primary leakage modes and mechanisms of metal tubings.Research reveals that fatigue-induced leakage is the most prevalent failure mode，initiated by factors such as loosely braided wire mesh，manufacturing defects in the bellows，additional vibrations or resonance due to improper type selection，and stress concentration during assembly.Crack propagation exhibits multi-origin fatigue characteristics.Corrosion-induced leakage primarily stems from stress corrosion cracking and localized pitting，where the synergistic effect of corrosive media and residual stress leads to brittle fracture or penetrative corrosion pores.Leakage from welding defects is predominantly associated with process-related issues such as oxide film inclusions in TIG welding and undesired flow of brazing filler metal，resulting in the formation of micro-channels.Mechanical damage leakage involves wall thinning caused by puncture during manufacturing or interference wear during operation，while fretting wear arises from long-term contact between the wire mesh and the bellows，leading to progressive damage.