本文在最新植物区系资料的基础上，利用北京市植物多样性本底调查研究的成果，对北京地区木本植物区系的种类组成、地理成分（科、属、种3个层次）等进行了系统的分析。分析结果表明，北京市有野生木本植物266种，隶属于46科109属。其中裸子植物3科6属9种，双子叶植物42科102属256种，单子叶植物1科1属1种，科内属种的分布极不平衡。科、属、种的区系地理成分复杂多样，科的分布区类型以温带分布类型占优势，其次是世界广布和热带分布类型；属的分布区类型以温带成分占优势，其中北温带分布型所占百分比最高，反映出该区系的温带性质；种的分布区类型中国特有分布的种数最多，其次是温带亚洲、东亚分布类型，其中中国特有分布类型主要以华北分布占优势，其次为东北-华北分布、华北-华中分布。此外，该区系木本植物区系地理成分的渗透性、交汇性和过渡性较明显。

This paper is concerned with analysis of the composition and geographical elements of the flora of Xylophyta in Being, using principle of florology based on the latest floristic data and the results of the investigation of the diversity of the plant in Beijing. There are 266 species of Xylophyta, belonging to 109 genera and 46 families, among which Gymnospermae have 3 families, 6 genera and 9 species, Dicotyledoneae have 42 families, 102 genera and 256 species and Monocotyledoneae have 1 family, 1 genus and 1 species, and the composition of the families is very imbalanced. Analysis of the floristic elements based on families, genera and species shows they are complex in Beijing. Temperate element is dominant in families, then Cosmopolitan and Tropic floristic elements. Temperate element make significant dominant in genera , in which the percent of North Temperate distribution is the highest , the species number of Chinese Endemic distribution elements is most in species , secondly Temperate Asia and E. Asia distribution elements, it is indicated that the flora has some typical characteristics of warm - temperate deciduous broad-leave forest. North China distribution is dominant in Chinese Endemic distribution, then Northeast China-North China and North China-Central China distribution. Besides, the permeation, intersection and transition of the flora are obvious.