The invention discloses a method for setting full-length tension of a cold rolling processing line. The method for setting full-length tension of the cold rolling processing line includes obtaining of a set tension value. The obtaining of the set tension value includes the following steps that a record set conforming to the steel type and the width value of incoming steel rolls is found out in a tension list; the thickness section of the thickness of the incoming steel rolls in the record is found out and composed of two adjacent thicknesses in the record; a tension value which is in the record and corresponds to the thickness close to the thickness distance of the incoming steel rolls in the two adjacent thicknesses is selected as the set tension value. According to the method for setting full-length tension of the cold rolling processing line, band steel has proper and stable tension, the problem that frequent variation of tension caused by variation of steel types and specifications among rolls in the incoming steel rolls is solved and thus, the quality and the productivity of steel coil products are improved.