The structural characteristics of chironomid (Diptera: Chironomidae) community in Mingzhu Lake of Chongming Island, Shanghai, China were studied from July 2006 to April 2008. A total of eleven chironomid species belonging to 10 genera and 3 subfamilies were collected, among which, Propsilocerus akamusi and Microchironomus sp. were predominant. Based on clustering analysis (CA) and importance value (IV), it was found that the dominant species shifted seasonally, with Microchironomus sp. in spring and summer, Tanypus chinensis in autumn, and P. akamusi in winter. There was a significant seasonal difference in the Shannon-Weaver diversity index (H') of the chironomid community, with the lowest in summer and higher in the other three seasons. The H' was significantly correlated with species richness (S) and evenness (J), and more strongly governed by J. The average density and biomass of the chironomid community were the highest in winter, with a minimum density in autumn and a lower biomass in the other seasons. Among the three dominant species, P. akamusi and Microchironomus sp. had more obvious seasonal fluctuations in their population dynamics than T. chinensis. Based on the bioassessment methods of water quality, e.g., H' and Hilsenhoff biotic index (BI), the Mingzhu Lake was considered to be moderately organically polluted and eutrophicated.