Abstract: Elaborated here in the paper are the main manufacturing processes for the bimetallic composite pipe. The formation principle of the hydraulically-formed bimetallic composite pipe is studied as the focus,and the formulas for the forming pressure and the liner tube dimensions are presented. Moreover the key factors as affecting the length of the liner pipe are analyzed. The variation of the liner pipe dimensions are also analyzed via relevant actual cases. It is revealed via the analysis that after being clad,the length of the liner pipe is shortened,and the original length and D/S of the liner pipe act as the main factors affecting the after-cladding final length;and that the calculated value of the after-cladding length of the liner pipe is basically in compliance with that of the measured value,which means that the former is slightly bigger than the actual shortening amount.