The present invention discloses an improved second-generation sequencing random label linker production method, which is characterized in that a Spacer modification capable of preventing the extension of a polymerase is introduced into a linker primer P7 in linker production; in a linker extension step, the extension is terminated after the polymerase encounters the Spacer site of a P7 template chain, and a 5' protruding terminal segment is leave; in the subsequent enzyme digestion step, the protruding terminal including the Spacer site is removed with endonuclease so as to produce a complete linker; and the residual un-digested linker being subjected to the incomplete enzyme digestion retains the long 5' protruding terminal.