Cross-border ethnic marriage is a special form of marriage that is found in border are-as.Although there is a historical basis and it is sanctioned morally, it is characterized by loose u-nions with no legal certification.This eventually has impacts,either positive or negative,on social man-agement and social stability in the frontier region. In the areas along the long border of China, the phenomenon of cross-border ethnic marriage does not lack written documentation,and appears in va-rious kinds of media.However,in terms of the cur-rent focus of domestic academic circles, the phe-nomenon of cross-border ethnic marriage in the Si-no-Vietnam border area is of particular concern. Thus,this area has become one with typical case studies of cross-border ethnic marriage in China's border areas.Cross-border ethnic marriages among the frontier people who live in the Sino-Vietnam border area is a historical phenomenon.However,it was not until after the founding of New China (1949) that cases of cross-border ethnic marriages were systematically registered,and the data became more accurate.However, because of the mobility and hidden nature of the people involved with cross-border marriages,it makes the statistical data in the China-Vietnam border area less reliable.In-stead of having specific data,we can only have es-timates.