Abstract: Fuel assemblies (FA) are core components in nuclear reactor,including PWR FA and BWR FA. FA can generate many defects during the lifetime in reactor, including corrosion, leakage, twist and deformation. The sipping inspection can be used to judge whether the FA is leaking or not;ultrasonic inspection can be used to locate the leaking fuel rod without dismantling the FA;eddy current technology is usually used in the inspection of the leaking fuel rod and measurement of the oxide layers. Damaged fuel assembly can be used after necessary repairing.