Vietnam has just celebrated the 40th anniversary of its national reunification (1975-2015). Over the last 40 years, Vietnam has experienced great changes in life and these comprehensive changes can be seen clearly through the development of languages. As special social phenomena, languages in Vietnam are deeply influenced by social context and therefore have adapted accordingly to perform their communication functions. As the national language, Vietnamese is the language that has been mostly affected by the impacts of the country's reunification and integration process. Taking a look at the whole thing in the opposite direction, it can be seen that Vietnamese is the only language, with its function as the national language, that can fully reflect all the changes taking place in the social life of Vietnam in the past 40 years.