Cable bridges developed earlier in China. This kind of bridge is usually built in a canyon, with steep cliffs on both sides, so it is not easy to be a pier in deep-water rapids. As a result, people in mountainous areas use suspended cables as bridges in their life and practice, and cable bridges flying in the air are born. There are many kinds of cable trays. According to materials, there are mainly rattan bridges, bamboo cable bridges and iron cable bridges. According to ancient records, the iron chain bridge appeared in China during the Northern Wei Dynasty. Iron cable bridge was invented by China people on the basis of bamboo cable bridge and rattan cable bridge. The most famous railway bridge in ancient China was located on the Dadu River in Luding County, Sichuan Province, and became Luding Bridge. From the point of view of manufacturing and erection, this bridge can be regarded as a representative of the iron cable bridge in the history of the world. And because there is a heroic story of the Red Army "flying over Luding Bridge", Luding Bridge is even more famous in the world. Luding Bridge is a suspension bridge built by Emperor Kangxi of Qing Dynasty. 1705, in order to unify the motherland and solve the obstruction on the road leading to Tibetan areas in Han areas, Emperor Kangxi ordered the construction of the first bridge on the Dadu River. After one year's construction, the bridge was completed at 1706 yuan. Emperor Kangxi took the meaning of "Lushui" and "Pingding" and wrote "Luding Bridge" in calligraphy. Since then, Luding Tiesuo Bridge has become a link between Tibet and China, hence the name Luding County. This royal monument still stands at the west bridge today. Qiaodong 1709 also has an inscription on Luding Bridge.