The invention provides an adjustable long-edge soldering iron for a two-channel packaging machine. The adjustable long-edge soldering iron comprises a soldering iron body. At least one heating block is arranged beneath the soldering iron body, and springs are arranged between the soldering iron body and the heating blocks. The soldering iron body is provided with a plurality of screw holes, first bolts penetrate into the screw holes, and the first bolts penetrate through the springs to be connected with the soldering iron body and the heating blocks. The first bolts are adjusted so as to adjust the high-low positions of the heating blocks in the operating process of the packaging machine, so that the heights are unified, and the heat-sealing effect is improved. Moreover, the front-back position of the soldering iron body can be adjusted by adjusting different positions of second bolts in long slotted holes, and thus the requirement for different heat-sealing positions can be met. The entire device is simple in structure, economical and practical; multiple defects existing in the prior art are overcome, and highly industrial utilization value is achieved.