According to the view of circumstantialism, ethnic identity will be changed with situations and caused the shift of ethnic boundary at the same time. So the main purpose of this essay is to analyze the shifting process of ethnic identity for the women who intermarried with Hokkien or Hakka people. This issue might involve the relationship of ethnic groups between Hokkien and Hakka people in Taiwan and the roles that women should act in the family under traditional norms. The concept of ethnic identity includes ethnic acknowledgement of themselves and their children, acculturation in the course of life and the dialect education of children and so on. This research chooses 12 women, 6 of Hakka people married with Hokkien people and 6 of the Hokkien people married with the Hakka people, to be interviewees through their stories about the ethnic groups of Hokkien/Hakka in their life before and after the marriage. The result of this study is: the ethnic self-identity of interviewees comes from determined blood relationship, but will be changed in different situations. Intermarriages will be the foundation of multiple identity. Then, interviewees are acculturated with different ethnic culture, especially the women must be adapted to the husband's family. The aspects of acculturation are different between the Hakka women and the Hokkien women, depend on the Hakka dialect, the stereotypes of Hakka people and the imbalance power relations of ethnic groups in the society. Moreover, interviewees generally undoubtedly assert that children's ethnic identity should depend on heritage from father, dialect education relying mainly on the orientation of market, and the Hokkien dialect is more important than the Hakka dialect, but both dialects are not so important as English. Intermarriages will definitely have different and multiple impacts on women's ethnic identity in different situations.