Abstract: The similarity of Quercus mongolica community in different sites was calculated. The coefficient of similarity is related to the distance between two sites in general. The shorter the distance between two sites, the bigger the coefficient of similarity is. Through the comparison among coefficient of similarity, Quercus mongolica communities could be divided into 4 types. They were Quercus mongolica communities in Daxinganling, Quercus mongolica communibies in Changbaishan, Quercus mongolica communibies in the west of Liaoning Province, Quercus mongolica communities in the south of Liaoning Province and Hebei Province.