The invention discloses a tube withdrawal method for a heat exchanger. The tube withdrawal method comprises the following steps of: performing drilling treatment on tube heads at the two sides of a heat exchange section of the heat exchanger through a drilling machine, and cutting tube walls until 5mm below a tube plate surface; pushing each heat exchange tube subjected to drilling treatment out of the tube plate at the lower end of the heat exchange section by 100 mm; and covering a sleeve tube hole in a tube withdrawal tool on a heat exchange tube extending out of the tube plate at the lower end of the heat exchange section, and withdrawing the tube through a crane. In a process of gradually lifting the tool withdrawal tool, an included angle of 30 degrees is formed between the inner surface of the tube covering hole, which sleeves the heat exchange tube, of the tube withdrawal tool and the tube wall of the heat exchange tube, so that clamping force is generated between the tube covering hole of the tube withdrawal tool and the tube wall of the heat exchange tube, and therefore, the heat exchange tube is withdrawn in a lifting process. According to the tube withdrawal method disclosed by the invention, through the lever principle, the tube withdrawal tool has enough clamping force during tube withdrawal, is not liable to drop, is easy to dismount after being withdrawn, does not need air-gouging processing, and has the advantages of being simple and convenient to operate, high in efficiency, simple in structure, easy to process and the like.