The invention relates to a heat-dissipation expansion structure of a galvanized quenching water tank. The heat-dissipation expansion structure comprises a quenching water tank, guide rollers and a galvanized plate; the guide rollers are erected on the upper side of the quenching water tank, and the galvanized plate passes through the guide rollers in a guiding mode; the galvanized plate below theguide rollers is immersed in cooling water of the quenching water tank, the number of the guide rollers is two and the two guide rollers are both horizontally erected on the upper side of the quenching water tank in parallel, and the galvanized plate is guided through the two guide rollers in sequence; and the galvanized plate between the bottoms of the two guide rollers is immersed in the coolingwater of the quenching water tank, and the capacity of the quenching water tank is increased to 6 m3. According to the heat-dissipation expansion structure of the galvanized quenching water tank, thecapacity of the quenching water tank is doubled, the flow area of the galvanized plate is quadrupled, thereby greatly reducing the temperature of the galvanized plate and ensuring the quality of theproduct; and the galvanized plate is completely flatten and then put into the cooling water by using the two guide rollers, thereby avoiding slight deformation of the galvanized plate and subsequent machining errors.