The bilateral relations between the Mongolia and the People's Republic of China have long been determined by the relations between China and the Soviet Union, Mongolia's other neighbour and main ally until 1990. With the rapprochement between the USSR and China in the late 1980s, Sino-Mongolian relations also began to improve. Since the 1990s, China has become Mongolia's biggest trading partner, and a number of Chinese businesses are operating in Mongolia.
Through history, Mongolia and China have waged many wars. China's Great Wall was constructed to ward off Mongolian and Central Asians attacks.Tuoba's Northern Wei Empire conquered all Chinese native land north of the Yangtze River.Han Chinese people have been lived mainly north of the Yangtze in that time. Mongols under Kublai Khan successfully conquered all of China in 1279, starting from Genghis Khan's conquest in 1211 and established the Yuan dynasty in 1271, and Mongolia later fell under control of the Qing dynasty of Manchu. With the fall of the Qing dynasty in 1911, Mongolia declared its independence after more than 200 years of foreign rule. Although many peoples of Inner Mongolia sought to accede to the new state, China retained its control over the area and invaded Mongolia in 1919. Consequently, Mongolia sought Soviet Russian support to reclaim its independence. In 1921, Chinese forces were driven out by White Russian forces led by baron R.F. von Ungern-Sternberg. Some months later they were driven out by the Red Army of the Russian Soviet Federative Socialist Republic, the Far Eastern Republic and pro-Soviet Mongolian forces. In 1924, the Mongolian People's Republic was proclaimed.
The People's Republic of China established diplomatic relations with Mongolia on October 16, 1949 and both nations signed a border treaty in 1962. With the Sino-Soviet split, Mongolia aligned itself with the Soviet Union and asked for the deployment of Soviet forces, leading to security concerns in China. As a result, bilateral ties remained tense until 1984, when a high-level Chinese delegation visited Mongolia and both nations began to survey and demarcate their borders. In 1986, a series of agreements to bolster trade and establishing transport and air links were signed. In 1988, both nations signed a treaty on border control. Mongolia also began asserting a more independent policy and pursued more friendly ties with China. Mongolia has always been suspicious that China wants to claim Mongolian territory, and concerned by fears of China's overpopulation pouring into Mongolian territory. 
In the Post-Cold War era, China has taken major steps to normalize its relationship with Mongolia, emphasizing its respect for Mongolia's sovereignty and independence. In 1994, Chinese Premier Li Peng signed a treaty of friendship and cooperation. China has become Mongolia's biggest trade partner and source of foreign investment. Bilateral trade reached USD 1.13 billion by the first nine months of 2007, registering an increase of 90% from 2006. China offered to allow the use of its Tianjin port to give Mongolia and its goods access to trade with the Asia Pacific region. China also expanded its investments in Mongolia's mining industries, giving it access to the country's natural resources. Mongolia and China have stepped up cooperation on fighting terrorism and bolstering regional security. China is likely to support Mongolia's membership in to the Asia Cooperation Dialogue (ACD), Asia-Pacific Economic Cooperation (APEC) and granting it observer status in the Shanghai Cooperation Organization.
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