Riparian zones are highly modified by frequent and intense human disturbances worldwide. Human-mediated disturbances often occur in concert with the proliferation of alien plants in the riparian zone, although their effect on alien riparian plants may differ among disturbance types (agriculture, urbanization). However, few studies in China have attempted to detect these effects on alien plants in riparian zone. The objectives of this study are (1) to compare the characteristics of alien herbal plant communities in different sections of a river (mountain section, agricultural section, and urban section) and (2) to explain the differences in alien plant communities that are caused by different types of disturbances (agriculture and urbanization).This study was conducted in 2009 in the riparian zone of the Yongding River in Beijing. The river stretches were categorized into three river sections based on the human-mediated disturbance types in that stretch of the river: mountain section (natural section without disturbance), plain section (agricultural disturbance), and urban section (urbanization disturbance). Using the transect method, 11 study sites were set up in this three river sections. The results show that the vascular herbal flora of the study area comprises 101 species from 72 genera and 27 families, including 29 alien plant species from 28 genera and 13 families. Alien species represent 28.7% of the total herbal flora, of which 82.4% originated from America and Asia. The species composition and dominance index of alien riparian plant communities change significantly among the three river sections. The percentage of alien species increases from 20.9% in the mountain section to 30.2% and 25.5% in the plain and urban river sections, respectively; the dominance index increases significantly from 12.1% to 13.4% and 17.5% in the plain and urban river sections, respectively. The composition of alien riparian plant communities inferred from the life cycle of the plants also shows significant difference among the three river sections. Perennial species are the most abundant in the mountain section (66.7%), while they are represented by 46.2% and 30.8% in the plain and urban sections, respectively. In contrast, the highest percentage of annual species is found in the urban section (69.2%) followed by the plain section (53.8%) and the mountain section (33.3%). The plain section is greatly affected by agriculture, where the alien riparian plants are mainly dominated by agricultural weeds such as Leersia japonica and Aster subulatus. The urban section is strongly influenced by the disturbance from rapid urbanization, in which the percentage and dominance index of invasive plant species are high. The typical invasive plants are Amaranthus retroflexus and Eleusine indica. These results indicate that the species composition of alien riparian plants differs among river sections and they are affected by different types of human-mediated disturbance (agriculture, urbanization). Our results also indicate that alien riparian plants may become predominant and spread further in the riparian zone due to human activities such as rapid urbanization and agriculture.