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Betula davuricaand deciduous Quercusforests are among the principal forest types in Northeast Asia. They are found throughout continental Northeast Asia and in some mountainous regions of Central Honshu and eastern Hokkaido in the Japanese Archipelago. B. davurica–Quercus crispulaforests in Japan are significant for understanding the phytogeography of Japan and Northeast Asia. However, their relationships with B. davurica–Quercus mongolicaforests in continental Northeast Asia remain poorly understood. We compared the species composition of B. davurica–Q. crispulaforests of Japan, with those of Q. crispuladominant forests and B. davurica–Q. mongolicaforests using phytosociological methods. The results suggested that B. davurica–Q. crispulaforests of Japan had a significant number of species common to the order Lespedezo bicoloris–Quercetalia mongolicae and the class Querco mongolicae–Betuletea davuricae in continental Northeast Asia than in other associations in Japan. Furthermore, our results showed that associations between B. davuricaand Q. crispulaforests in Central Honshu and Hokkaido are related to different orders in continental Northeast Asia. The relations of the associations between Japan and the continent are considered to have been caused by the environmental similarities, the histories of taxa, and the changes in vegetation distribution.