This paper bases on the first-hand materials of field investigation,analyzes and summarizes the usage of ethnic language in the China-Vietnam boarder town Dulong, summarizes three conclusions: ethnic language and Chinese language will be long-term used and harmonious development at the same time in Dulong town. The national language policy of our country should consider the particularity of cross-border languages. Cross-border ethnic language harmony will provide language services to "one Belt,one Road" strategy.