Urban habitat fragmentation caused by urbanization has had a negative impact on urban wildlife diversity. As the connected green space in the city, the ecological corridor plays an important role in the biodiversity conservation in the process of urbanization. As an important part of urban plant diversity, spontaneous plants provide resources for the survival of native animals and play a key role in the construction of low-maintenance plant landscape. In this study, we determined the overall composition of spontaneous species in the Wenyu River-North canal ecological corridor in Beijing, explored the changes of species composition and diversity characteristics of spontaneous plants with urbanization gradients, and analyzed the adaptability of different spontaneous species to urbanization. A total of 195 plant species were recorded which belonged to 156 genera and 73 families, and most of them were herbaceous plants. There was no significant difference in alpha-diversity of spontaneous woody plants at different urbanization levels. However, the alpha-diversity of spontaneous herbaceous plants at medium urbanization level was significantly higher than that at other levels (P < 0.05). With the increase of urbanization index, the beta-diversity of woody plants, annual herbs and biennial herbs increased, and the beta-diversity of perennial herbs, invasive plants and exotic plants decreased. The mean niche width with urbanization gradient was ranked as invasive plants > native plants > domestic exotic plants > foreign exotic plants. According to the niche width, the ecological corridor autophytes were divided into high adaptability type, moderate adaptable type and low adaptable type. We screened some native plant species with similar adaptability to the 15 invasive plants according to niche overlap. The results can provide references for constructing stable low-maintenance spontaneous plant communities, that can resist the spread of invasive plants, so as to bring the function of biodiversity conservation of urban river ecological corridors into full play.