To detect potential changes in properties of weed communities in fields of GMHT rice Bar68-1, trials were carried out from 2007-2008 at Changsha, China with conventional indica rice D68 served as control. The average richness of weed community measured by species accumulation curve tended to be identical in the fields of Bar68-1 and D68 as the number of sampling points increased. There were no significant differences (p &gt; 0.05) in diversity indices which included numbers of species(S), Shannon-Wiener (H'), Pielou evenness (J'), Simpson diversity (D) and evenness (E) indices. Species composition for these two weed communities was roughly comparable. The top four weed species, sorted by individual abundance, were Monochoria vaginalis (Burm. f.) Presl ex Kunth, Lindernia procumbens (Krock.) Philcox, Cyperus diformis L. and Juncellus serotinus (Rottb.). B. Clarke in the fields of Bar68-1 and D68. ABC curves showed that the weed communities were 'unpolluted'. The data above confirm the hypothesis that the difference between the effect of GMHT rice Bar68-1 on biodiversity of weed in paddy fields and that of non-GM rice D68 was not significant.