There is a special time category in Mongolian and Korean, which is obviously different from the general time category. In Mongolian, this category of tense is reflected through the suffix of adjectival verb, while in Korean, it is reflected through the adnominal suffix. This paper studies it from the aspects of concept, grammatical features and grammatical functions. This kind of ending has obvious nominality, which can be inferred to originate from the gerund ending. The study of this tense category is of great significance for the establishment of the grammatical category types of Altai languages and the study of the homologous relationship between Mongolian and Korean.