The article deals with the study on the Soviet and Russian historiography of the Sino-Mongolian relations since the second half of the XXth century until now. During the Soviet period, the Sino-Mongolian relations were examined regarding the Sino-Soviet relations. However, in the 90s of the XXth century Russian researchers focused their attention on the Sino-Mongolian relations in particular their comprehensive development. Nowadays the research on the Sino-Mongolian relations is relevant for strengthening relations between Russia, Mongolia, and China.