Abstract: In order to test whether plant functional group diversity affects plant biomass, microbial biomass and nutrient retention in constructed wetlands, five plant functional group richness treatments (including unplanted treatment, treatments planted with one, two, three and four functional groups, respectively) were established. The plant biomass, microbial biomass carbon and nitrogen, as well as organic carbon, NH+4N, NO-3N and available phosphorus contents in the filled material were analyzed, respectively. The results of the one-way analysis of variance (ANOVA) indicate that plant biomass, microbial biomass carbon and nitrogen are significantly increased with the plant functional group richness (P 0.05), while the contents of NH+4N of NO-3N are depended on whether the treatments are planted or unplanted. Correlation analysis reveals that the plant functional group richness is positively related to plant biomass and microbial biomass carbon and nitrogen, and as well as the NO-3N content, and the microbial biomass carbon is positively related to the contents of NH+4N of NO-3N. The present study highlights the importance of plant functional group diversity in improving plant biomass, microbial biomass carbon and nitrogen in a constructed wetland.