The surname Cai is the 44th most common in China, but the 8th most common in Taiwan province.
According to historical records, King Wu of the Zhou Dynasty defeated King Zhou and established the Western Zhou dynasty (c.11th century �C 771 BC). King Wu granted titles and territories to his brothers. Shu Du, one of his brothers, was crowned in Yucai (where Shangcai in Henan province is today), so Shu Du was later called Uncle Cai. Hu, the son of Uncle Cai, established the capital in Shangcai.
During the Spring and Autumn Periods (770BC�C476BC), Cai State migrated several times after being invaded by Chu State, eventually settling down in Zhoulai (where Fengtai in Anhui province is today) at a place called Xiacai. King Hui of Chu State conquered Cai State in 447 BC, and the people took the surname Cai in memory of their lost state.
The Cai clan migrated twice. During the Huangchao Uprising (875 BC) at the end of the Tang Dynasty (618-907 BC), the Cai clan migrated to Guangdong, Fujian and Taiwan. Another movement occurred when Zheng Chenggong, (a national hero), moved military officials carrying the surname Cai with their families and relatives to Taiwan.
Later, the descendants of the Cai clan in Taiwan began to multiply.
By People's Daily Online