Semantic role ‘Instrument’ in linguistics, which is defined as means or materials by which the action (verb) is implemented. It is one of the major arguments which are involved in action. In Russian, ‘Instrument’ is usually expressed in the form of a instrumental case, and in the field of education the meaning of the ‘Instrument’ is presented as the most typical usage of instrumental case. However, ‘Instrument’ in Russian is also expressed in the form of prepositional phrases. This study is aimed to prove the synonymy of Instruments in instrumental case and prepositional phrases by identifying their semantic and syntactic characteristics. In a broad sense, ``Instrument`` includes inherent instrument, materials, and means. All of these are used in the process of action and are involved in performing of it, so it can be said that they are synonyms with semantic proximity. Instrument-argument, depending on lexical meaning of verb and how it is used, is expressed in a prepositional or non-prepositional form. In the aspect of expression, instruments are also considered synonymous. This study can specify explicitly the role of Instrument and consider the function of preposition in case carefully. At the same time, it can be said that it helps to better understand the semantic structure of action.