Most of the population in Big Hsi-lo area in Yunlin county immigrated from Zhaoan county in Zhangzhou Fujian. This is also the biggest Fujian Hakka island in Taiwan. There are four Hakka counties in Zhangzhou. But only in Zhaoan, the Hakka makes up one-third of the population of the county. Therefore, it occupies an important place in Zhangzhou Hakka. We study the language distribution of Zhaoan county by fieldwork, and consult the document about the population and language distribution in Zhaoan. According to these data, we draw the language boundary between Minnan and Hakka. The precision of the boundary covers the range of natural villages. We classify the dialects of Hakka and Minnan, and mark off their geographical distribution as well.