May 31, 1960 (, Boxer In May, the seventh day), and Mongolia signed a treaty of friendship and mutual assistance.

1960 31, 2009, the Sino-Mongolian Treaty of Friendship, Cooperation and Mutual Assistance signed in Ulaanbaatar. Became effective on October 12 of the same year. Contracting Parties: mutual respect for sovereignty and territorial integrity, mutual non-interference. Internal affairs, on the basis of equality and mutual benefit, to consolidate and develop the friendly and cooperative relations.