Compared with western languages, Mongolian and Korean, as Oriental languages, have their own unique characteristics. There are many studies about the number category of Altaic languages, including Mongolian and Korean. However, most of the previous studies have confined the number category to the framework of Indo European linguistics to analyze and understand its significance. This type of approach will not properly clarify the complex linguistic facts of the number category in Mongolian and Korean. Taking the number category of Mongolian and Korean as the research object, this paper makes a brief analysis from three perspectives: the opposition of numbers, the consistency of numbers, and the grammatical function of plural markers. By giving specific examples, it reanalyzes the previous views on number category, aiming to summarize the characteristics of number category, It also provides reference for the study of the number category and grammatical characteristics of other Altaic languages.