In order to solve the problem that the structure welding and composite nozzle of 5 kN engine could not be detected,the industrial CT detection technology was studied.Based on the analysis of the difficulties in the conventional methods of detecting complex structure weldings and composite nozzles,and taken the advantages of industrial CT detection technology,such as strong penetration ability and not affected by the complex structure of the workpiece, the structures of electron beam weldings,argon arc weldings and composite nozzles in 5 kN engine products were tested,and good detection results were obtained.The test results show that the industrial CT detection technology can solve the inspection problems of structural welding and composite nozzle in 5 kN engine products,realize the identification,location and measurement of defects such as porosity, incomplete penetration, delamination and crack,and provide the basis for welding quality evaluation.