Based on the data of spontaneous urban vegetation,the human impacts on urban flora have been discussed in this paper. The conclusions are: (a)As a result of human activity,the urban flora with regard to its spectrum of dominant families is different from that of natural vegetation,but shows rather similar characters among different cities.(b)The ecological characters of the urban flora are strongly influenced by the urban climate and soil. (c)The expand of urban land use and its influence on urban habitats as well as some measures for greenery patches management are threatening the existence of some species in the urban area.