Abstract: The origin and the migration of Monochamus Guér on the earth,the origin of Chinese Monochamus fauna and its biogeographical relation to other areas,and geographical distribution of five species which do serious damages to the forests in China are discussed.It is indicated as follows: (1) Monochamus is a typical tropic and subtropic group.The global distribution of this genus shows that 59.3% of all species are distributed in Ethiopian,26% in Oriental,8% in Neoarctic,6.7% in Palaearctic and none in both Australian and Neotropic. (2) Monochamus should originate from Ethiopian during Middle to Late Cretaceous.Some of Monochamus species migrated from Ethiopian into Oriental during Early to Middle Tertiary through Arabian and Iranian areas covered with tropic rain-forests then.Since Late Tertiary,the immigrants in Oriental had spread gradually into Palaearctic through the east of China.And ancestors of Neoarctic species should immigrate from Eurasia through the Bering Land Bridge during Cenozoic,but the exact immigrating time hasn't been determined yet. (3) Since Early to Middle Tertiary,the immigrants in Oriental had tended to spread up to the north. (4) Monochamus fauna in China has evolved from:(a) Endemic components.They evolved from China,but their ancestors immigrated from Ethiopian through India and Indo-China during Early to Middle Tertiary. Some of China endemic species had spread into the north of China.(b) Indian and Indo-Chinese components.The species originated from India and Indo-China immigrated into South China during Late Tertiary to Quaternary,some of which spread into North China. (5) Biogeographically,China Mainland is closely related to Japan,China Taiwan,India,Indo-China,Siberia and Europe.All Monochamus species of Siberia and Europe are also distributed in China.China Mainland and Japan as well as China Mainland and Taiwan share some of Monochamus species. Japanese endemic species (Palaearctic species) may probably do damages to the forests of North and Northeast China,and endemic species (Oriental species) of Taiwan are also dangerous to the fcrests of South China (Mainland).There are a lot of species which are the same between South China,India and Indo-China,but endemic species of India and Indo-China might be carried into South China and do damages to the forests there due to (3) above.Therefore,import log and timber from Japan,China Taiwan,India and Indo-China must be in strict quarantine. (6) There are five species that do serious damages to the forests in China.M.bimaculatus,whose northest distribution border is at Nan Lin (about 25°N),belongs to typical Oriental components.This species mainly bores broadleaved trees in South China.M.alternatus is also an Oriental species,but its northest distribution border is at Chin Lin (about 33°N) in West China and at Beijing (about 40°N) in East China.M.alternatuslives on broadleaved and secondary coniferous trees,but mainly on masson pine Pinus massoniana Lamb.in China.The opposite is the case with M.urussovii,it belongs to a typical Palaearctic species,whose southest distribution border is at Chin Lin.This species bores coniferous trees.The similar pattern is found to be the case with M.sutor and M.saltuarius.