The article deals with the use of prepositions of Old Chinese in the texts of Tang bianwen. It is the Literature of secular or buddhistic type, the language of bianwen as well as yulu is close to the colloquial language of the Tang. The difference in the use of prepositions as well as the difference in the use of constractions, most clearly shows transformation in the grammer of the Chinese. The paper describes preposition of Old Chinese, their functions in the texts of bianwen, theare is noted the difference in the use. The conclusion is that the prepositions of Old Chinese are wildspread in this type of Literature, part of them in new functions.