The research purpose is to study Mongolian dialects within the framework of the language-saving policy and to define their language vitality and endangerment based on some of the international criteria. In this research, we used several sociolinguistics methodologies such as sociological survey, collecting and developing the materials, investigative and statistical methods, comparing logical, correlation, analytic, synthetic methods, induction, and deduction. Here the authors tried to study the Language Vitality and Endangerment/Language Vitality Assessment (UNESCO 2003), which is used more commonly and frequently at the international level, to define Mongolian dialects’/languages’ vitality,
 Finally, our research was made on eighteen Mongolian dialects such as khotong, darkhad, khalkh, Kazakh, bayad, uzemchin, torguud etc…. As a result of the research, most of the Mongolian dialects included in the categories such as don’t heritage their languages to the next generation or severely endangered. During the research, we observed that several factors such as demography, politics, geography, social and economic situation, psychology, population movement, government policy on language, and others are influencing the extinction of the minority languages of the nations and ethnic groups.
 Eventually, it is necessary to study, save, revitalize, and document the dialects and pass them to on the next generation.