Abstract: The present paper deals with the studies of taxonomic treatments, phytogeography and origin of the genus Pseudotsuga Carr. 2 sections, 6species and 1 variety have been accepted. Sect. Sina involves 5 species: P. forrestii, P. brevifolia, P.sinensis, P. japonicc, P. macrocarpa;while.Sect. Pseudotsuga is provided only with 1 species and 1 variety: P.menziesii, P. menziesii var. glauca. The first section covers a typical areaof "E. Asia & N。America disjuncted", and the second one is endemicto western N. America. Geograpic distribution of the genus and vicariouspattern of affinis species are discussed, by means of the related datafrom cytology and paleobotany, the following proposals are presented:1.Sect. Sina is a primitive group, Sect. Pseudotsuga is an advanced one, which may be originated from an ancestral Sina group for its 12 pairsof chromosomes happened to be reanged;2。Pseudotsuga might be a genusdeveloped in North Pacific Floristic area, and originated in E. Asia, while western N. America can be regarded as a developing center of the genus.

Key words: Pseudotsuga, Taxonomy, Phytogeography, Origin