Based on the results of investigation of Arhorchin Mongolian folk medicinal plants and related knowledge system, the present paper discussed the interrelationship between folk plant medicine and Mongolian medicine as well as Chinese herbal medicine by the items of plant species, medicinal parts, treating disease and administering methods. The results show that there are some consistency between folk medicine and Mongolian medicine as well as Chinese herbal medicine, and there are also some other inconsistency. Consistency between folk medicine and Mongolian medicine may be illustrated the fact that the Arhorchin Mongolian folk medicinal knowledge and Mongolian medicine are belongs to same system. Consistency between folk medicine and Chinese herbal medicine are illustrated the fact that knowledge exchange and cultural infiltration between Arhorchin Mongolians and Han nationality. Inconsistency may be illustrated richness and exploration value of folk medicinal knowledge.