Abstract: Summarized in the essay is the practical experience in using the 3D surface inspection system over the past two years, and studied is the application of the said system to inspection of steel tube outer surface defects. A comparison between the inspection effect of the 3D inspection system and that of the magnetic flux inspection system is conducted to identify the separate advantages and disadvantages of each of the two. Focused on are the problems as commonly-encountered with during the operation process of the 3D inspection system, and the system’s source of false alarms, and relevant solution. It is emphasized that 3D inspection system has met the goal of preventing serious defect-missing, being a good supplement to the NDT processes like the magnetic flux inspection, the UT inspection and the eddy-current testing, etc.