[Aim] Galinsoga quadriradiata is a new invasive plant in the Inner Mongolia Autonomous Region, with an expanding range and an increasing size of population in Hohhot City. To understand the impact of the invasion of G. quadriradiata on local plant diversity that can provide early warning and theoretical basis for timely prevention and control, the plant diversity in the invaded areas was examined.[Method] Based on the surveys and mathematical statistics, the differences in four indices were analyzed in 21 quadrats:species richness (S), Simpson index (D), Shannon-Wiener index (H) and Pielou index (J).[Result] There were 73 plant species identified in the invasive quadrats, belonging to 55 genera and 25 families, in which 18 species were Compositae, accounting for 24.66% of all the species. The second most diverse groups were Gramineae and Chenopodiaceae accounting for 17.81% and 5.48%, respectively. In these invaded regions, the important values (IV) of G. quadriradiata showed varying degrees of increase, which characterized by IV raise followed to the addition of relative density, relative frequency and relative coverage. Compared with the control plots, the S, H, D and J showed a similar downward trend in invaded plots, the maximum declines range were 65.2%, 78.6%, 62.2%, and 72.6%, respectively, all of which H index fell sharpest. The relationship between the IV and the above mentioned four indices (e.g., D, H and J) showed that the four indices decreased with the raise of the IV index of G. quadriradiata, when the IV index was greater than 0.551, the H index was reduced significantly (P<0.05). Similarity, when the IV index was >1.10, the D and J indices were significantly reduced (P<0.01),[Conclusion] The invasion of G. quadriradiata adversely affected the local plant diversity in Hohhot, and preventive and control measures should be launched in a timely manner.