This article is dedicated to determination of priority vectors in China-Mongolia relations in the early XXI century. Special role is assigned to cooperation in the political, economic and humanitarian spheres. A number of criteria that allow speaking of the level of intergovernmental relations in each indicated sphere is reviewed. For assessing political cooperation, the author considered the conceptual approaches of the PRC and Mongolia towards bilateral diplomacy. In this context, analysis was conducted on Mongolia's Third Neighbor Policy and China’s Partnership Diplomacy Strategy. The article explores the interaction of China and Mongolia on the global, regional and bilateral levels. In economic regard, the assessment of cooperation of the two countries was carried out on the basis of mutual trade turnover and the volume of foreign direct investment. In the humanitarian context of bilateral cooperation, the author studied the intensity of mutual tourism flows, student and academic exchanges. The analysis was performed within the framework of neorealist paradigm, in the categories of systemic approach for viewing China-Mongolia relations as a unified system consisting of three subsystems. The author's special contribution consists in the attempt to assess bilateral cooperation between China and Mongolia in the early XXI century, with consideration of the impact of the ongoing transformations within the system of international relations on the regional level. The conclusion is made that despite a number of threats that stem from PRC’s proactive policy in Eurasia, as well as the objective dissonance in socioeconomic development of the two countries, the cooperation in the indicated areas in the early XXI century few has been developing steadily. In the twenty-first century. It had a positive impact upon China-Mongolia relations overall.