In modern Kazakh language, one of the Turkic languages, historical reduplicatives are widely used. Currently, double words in written monuments written in ancient Turkic languages are used in the Kazakh language without any changes. Since reduplicativesare common among the ancient Turkic languages in the ancient Uighur language, our article considered reduplicativesin the modern Kazakh language and the ancient Uighur language. The article found that some words were used as is, without anychanges in sound, structural and semantic terms, which is confirmed by examples. It has been shown that some reduplicativesused since the time of the ancient Uighurs have undergone minor changes, that is, some of them have undergone changes in the secondword in the modern Kazakh language.The purpose of the article is to find out, no matter how many centuries have passed between them, some words in two Turkic languages (one old, one modern) are used in both languages as is. To reveal and show the continuation between the two Turkic languages. The article is of great scientific and practical importance in studying the process of determining the territory in which the ancient Turkic languages were used, and step-by-step changes. In the scientific work, methods and techniques of comparativeanalysis, grouping, translation were used, an analysis of the origin of some words widely used both in the ancient Uighur language and in the modern Kazakh language was achieved. While writing this article many works in the ancient Uighur languagewere used.The relevance of the article lies in the fact that this topic has never been used in Kazakh science in the Kazakh language and has not entered scientific circulation. The article can be used as an auxiliary textbook inthe disciplines “History of Kazakh literature”, “History of Turkic literature”, “Introduction to Turkology”.