As early as 1981, the color steel bridge of German OBO entered China Jinshan petrochemical plant for the first time, which has been kept in good condition so far. It can be seen that it has excellent service life. However, due to its high cost and complex process, the hot-dip galvanized bridge (the thickness of zinc layer is greater than or equal to 65um) is generally used in China, which is simple in process and cheaper than the color steel at that time. With the development of China's rough economy, the pursuit of quantity change, the simple production mode of bridge, with high returns, has attracted hundreds of thousands of manufacturers to manufacture, most of them are manual workshops. Vicious low price competition can start from the price obtained by the first manufacturer, and now it's sold at a discount of 50% or 30%, even many of the prices can't be guaranteed even the cost price. Manufacturers also sacrifice the strength and service life of products by directly reducing the thickness of iron sheet and zinc layer. So it can be seen that many bridges are corroded and have big belly during construction. In addition, with the increase of environmental protection in China, the cost of secondary galvanizing for traditional hot-dip galvanizing bridge needs to be increased again, so that the product quality is very uncontrollable. Color steel plate is a product of galvanized steel plate, which is made by two roll coating and two bake curing after surface chemical treatment. It is also produced in continuous production line, so it is also called color coated steel plate roll. Color steel plate not only has the properties of high mechanical strength and easy forming of steel material, but also has good decorative and corrosion resistance of coating material. Color steel plate is a new kind of material which is highly praised in the world. With the progress of science and technology, the enhancement of environmental awareness and the improvement of people's living standards, color steel plate has outstanding performance in all walks of life, and is favored by construction, home appliances, electromechanical, transportation, interior decoration, office appliances and other industries.