Cai surname is one of the surnames in China, and it is a typical multi-ethnic and multi-origin surname, which mainly comes from the changes of Ji surname, Yi surname and minority surnames. In the Western Zhou Dynasty, Cai was the ancestor. Cai ranked 155 among the hundred surnames in Song Dynasty. By the end of 20 13, the total population of contemporary Cai surnames has reached 5.52 million, accounting for 0.46% of the total population in China, and the total population ranks 44th among the surnames in China. The distribution of Cai surnames in China is mainly concentrated in Guangdong, Zhejiang and Jiangsu provinces, and a high proportion of Cai surnames have been formed in the southeast coastal areas.

The ancestor of the surname is, her name is Hu, also called Cai Zhonghu, her grandson, the son of Cai Shudu, and the second monarch of Cai, a vassal state of the Western Zhou Dynasty. After the destruction of the business, his brother and uncle were appointed to Cai and established Cai. After Zhou Chengwang succeeded to the throne, Cai Shu rebelled with Guan Shu and others, was exiled after failure, and died soon after moving the capital. Hu, the son of Cai Shu, changed his father's old habits and respected virtue and goodness. When the Duke of Zhou heard about it, he recommended him to be an official of the State of Lu. Duke Zhou suggested that Hu be sealed in Cai State to serve Cai Shu's ancestors and his descendants would take the country as their surname.