Abstract: Addressing the problem that since the early-developed code-stenciling machine has no automatic identification-correction system,and thus each time when adjusting the robot movement track as per steel pipe size change or during the robot code-stenciling process,some components like the jet are frequently damaged,it is proposed to add a servo control lifting mechanism onto the front arm of the original code-stenciling robot,and accordingly the stenciling parts like the jet as originally mounted on the said front arm are now removed onto the lifting mechanism. Thus when adjusting the robot movement track or during robot code-stenciling process,the servo control system is capable of checking the distances between the jet and the inner surface and the outer surface of the pipe to automatically control the lifting-lowering of the jet device so as to get the said distances within the set value range. As a result it is avoided to have the mechanism knocking against the outer or inner surface of the pipe,which brings about the high-efficient,intelligent,and safe and smooth running of the code-stenciling machine.