An improved manufacturing method for the hole-punching assembly of a hole-punching unit is disclosed. The method of the present invention comprises the following steps: (1) forming a plurality of aluminum balancing pieces with a rectangular shape by extrusion, and forming an indentation area on one side of each balancing piece; (2) forming an elongated slot by an application of stamping on the indentation area of each balancing piece; (3) obtaining a plurality of rectangular pieces (the number of which equals that of the balancing pieces), made of iron, and forming a row of holes by a single application of stamping on each rectangular piece; and (4) fitting each of the rectangular pieces onto the indentation area of a balancing piece, and connecting the balancing pieces together by screws or bolts. The manufacturing method can lower the production cost and simplify the production process of the hole-punching assembly.