Abstract: Various corrosions and defects possibly emerged in urea synthesizer were presented. The effective nondestructive testing (NDT) method according to damage mechanisms and mode of failure were also put forward. The applied NDT methods included visual testing, thickness measuring, magnetic particle testing, penetration testing, hardness testing, acoustic emission testing, metallographic analysis and metal magnetic memory testing. The application situation and characteristic of each NDT method applied in urea synthesize tower were introduced.