Abstract: To clarify the changes in phytoplankton communities in Chaobai River basin of Beijing, 17 sampling sites of periphytic algae were selected and two surveys were conducted in May 2021 and September 2021. Community structure was analyzed by applying the number of periphytic algae species and cell density, and the dominance index of the dominant species(Y) and dominant species turnover rate (R) were calculated. The niche width (B_i), niche overlap (O_ik) and overall relevance were used to analyze the niche characteristics of the dominant species. The results showed that a total of 109 species of periphytic algae belonging to 4 phylums and 41 genera were found and recorded in two phases. There were 8 dominant species (Y>0.2) of periphytic algae in all sampling periods. The niche width values of dominant species ranged from 0.140 6 to 0.420 9. The niche overlap values of the dominant species ranged from 0.055 1 to 0.897 1, and the overall correlation measurement results were significantly positive correlations. The dominant species were greatly affected by seasonal alternation, and the commonality of resource utilization among dominant species was relatively small. The structure of the periphytic algae tended to stabilize, and the overall development was toward positive succession. The research shows that periphytic algae, as a biological indicator, can respond sensitively to changes in environmental conditions. Based on the niche characteristics of the dominant species of periphytic algae, the community structure and succession characteristics of periphytic algae can be described.