Historical linguistics deals with language change. Historical linguistics is sometimes called diachronic linguistics, since historical linguists are concerned with change in language or languages over time. Sound change, analogy and borrowing have traditionally been considered the three most important (most basic) types of linguistic change. The study of loanwords, and of language contact more generally, is a useful way in tracing linguistic change in the past. Because borrowings are very important in Historical Linguistics studies, this study will be about the borrowing of Chinese words in the Old Uigur era writings. This study will try to reveal Chinese borrowings in the Old Uigur era and the reasons for them. Determining the reasons for the borrowing of Chinese words in the Old Uigur era, in which the most voluminous Old Turkish books were written, is the priority of this study. In addition to this, original and new language notes that are summarized from the documents where the borrowings are seen, make this study even more important. In this study, Chinese borrowings in the above-mentioned era will be investigated with historical linguistics methods and the results will be presented to scholars studying Turkish Language or linguistics. In this way, we will contribute something new to Linguistics and Turcology. In this study, we will investigate how Old Uighurs borrowed from foreign languages and whether the borrowings were prestige, reverse prestige or needed borrowings along with other reasons.