According to the understanding of the main art garden, in the evolution process of more than two thousand years, various forms of Zheng have been produced, and the string quality has also evolved and developed with the change of Zheng species. In this long history of more than 2,000 years, the change and development of the quality of the zither string is extremely slow.

In the history of Zheng, silk strings were mostly used, and there were also casings or chicken ribs. There are five-color strings wrapped around silk strings and red and green strings. Cui Xian refers to the green string, and Zhu string refers to the red string.