Previous studies almost hold the view that the Chinese translated Buddhist Scriptures are inclined to use a kind of particle just as syllabic complement and with no grammatical meaning due to its special literary style of 4-word one pause, and Yu(于/於) interposed between the verb and the noun is a case in point. But by means of the actual Sanskrit-Chinese comparative analysis of Saddharmapudarīkasūtra, we get the hope to modify the previous view, that is, in the Chinese translated Buddhist Scriptures, Yu(于/於) still acted as a preposition to introduce related nominal elements to the verb. Moreover, the direct correspondence of Yu(于/於) to the various inflectional ease forms of the nominal elements in the original Sanskrit text reinforced its attribute as a case marker.