Abstract: Aiming at the technical problems existing in the formation defects of weld after welding,several commonly used nondestructive testing technologies,namely structured light vision testing,ultrasonic testing,eddy current testing,magneto-optical imaging testing and infrared testing,are deeply studied.The basic principle,system structure,detection characteristics and respective application scope of the above detection methods are discussed.The research results show that each single detection technology has its own advantages and shortcomings,which can not meet the requirements of comprehensive detection of welds,and various detection methods can be combined to complement each other.