Abstract：Benthic diatoms are the main primary producers in river ecosystems. Understanding the impact of urbanization on the diversity of benthic diatoms has an important significance for urban river ecological management. In this study， the response of the traits， taxonomic and functional diversity of river benthic algae to urban disturbance was assessed using the rivers in Shenzhen as an example. We found there were significant differences in water quality conditions between urban and suburban sample sites. The concentrations of NH4+-N， NO2-N， TN， TP， and DOC in the urban sample sites were 3~20 times higher than those in the suburban group. The dramatic changes in the water environment had also led to changes in the biodiversity of river benthic diatoms. The species richness， Pielou index， and Simpson index were significantly higher in the urban group than those in the suburban group， while the functional evenness was significantly lower than that in the suburban group. Among the 21 diatom traits， 15 traits were significantly different between urban and suburban groups. Random forest model was further used to fit the relationships between the biodiversity of the benthic diatoms and water quality indicators， and the responses of diatom traits to urbanization were found to be more sensitive than other indicators， especially the four traits of size2， mobile， low profile guild and motile guild， and the explanation rate of these constructed random forest model could reach 40%~60%， while the models constructed for the biodiversity indices explained only about 15%~25% of the variance. TP and TN were the main factors affecting benthic diatom diversity in urban rivers. In the urban sample sites with high nutrient content， diatoms with larger size and mobile were dominant， while in the suburban sample sites with lower nutrient content， smaller， stalked diatoms living in a smaller guild were more dominant. Our study demonstrates the sensitivity of diatom traits in response to environmental change， and diatom traits are an important tool for assessing the ecological status of rivers.