The history of the expansion of “Russian Asia” in the 17th – 19th centuries is associated with the formation of a transboundary space that has absorbed migration flows and energy of Russian (Orthodox), Mongolian (Buddhist-nomadic) and Chinese (Taoist-Confucian) civilizations. The Russians were mentally and politically perceived by the Mongol elite as saviors. In the 19th– early 20th centuries Mongolia, turned into the Mongolian People’s Republic, which was under the formal suzerainty of China. International legal “inconsistencies” in the status of the MPR were eliminated by the decisions of the Yalta Conference of the Allies (February 1945), the Mongolian referendum followed by the recognition of its results by Chiang Kai-shek in 1946. The triangle “USSR – MPR – China” acquired a complete form with full international legal registration. The post-Soviet outlines were largely determined by the signing in 1993 of the Russian-Mongolian and in 1994 the Mongolian-Chinese Treaties of Friendship and Cooperation, the emergence of a “third neighbor”, the strengthening of China on trade and investment platforms. The signing in 2019 of the Russian-Mongolian Treaty on Friendly Relations and Comprehensive Strategic Partnership has politically strengthened the Russian-Mongolian vector, strengthening the overall strategic foundation of the triangle. The Mongolian sector, in terms of increasing China’s economic share and its influence in general, remains the “weak link” of the tripartite structure. The article analyzes the historical and modern realities of the interactions of the three states, the Russian and Chinese components, their political, financial and economic dimensions, the strengths and weaknesses of bilateral relations in the triangle.