Production of mutants with altered phenotypes is a powerful approach for determining the biological functions of genes in an organism. In this study, a high-grain-weight mutant line M8008 was identified from a library of mutants of the common wheat cultivar YN15 treated with ethylmethane sulfonate(EMS). F2 and F2:3generations produced from crosses of M8008 × YN15(MY) and M8008 × SJZ54(MS) were used for genetic analysis. There were significant differences between M8008 and YN15 in plant height(PH), spike length(SL),fertile spikelet number per spike(FSS), grain width(GW), grain length(GL), GL/GW ratio(GLW), and thousand-grain weight(TGW). Most simple correlation coefficients were significant for the investigated traits, suggesting that the correlative mutations occurred in M8008. Approximately 21% of simple sequence repeat(SSR) markers showed polymorphisms between M8008 and YN15, indicating that EMS can induce a large number of mutated loci. Twelve quantitative trait loci(QTLs) forming QTL clusters(one in MY and two in MS) were detected. The QTL clusters coinciding with(MY population) or near(MS population) the marker wmc41 were associated mainly with grain-size traits, among which the M8008 locus led to decreases in GW, factor form density(FFD), and TGW and to increases in GLW. The cluster in the wmc25–barc168 interval in the MS population was associated with yield traits, for which the M8008 locus led to decreased PH, spike number per plant(SN), and SL. Production of mutants with altered phenotypes is a powerful approach for determining the biological functions of genes in an organism. In this study, a high-grain-weight mutant line M8008 was identified from a library of mutants of the common wheat cultivar YN15 treated with ethylmethane Sulfonate (EMS). F2 and F2: 3 generations produced from crosses of M8008 × YN15 (MY) and M8008 × SJZ54 (MS) were used for genetic analysis. There were significant differences between M8008 and YN15 in plant height (PH), spike length (SL), fertile spikelet number per spike (FSS), grain width (GW), grain length (GL), GL / GW ratio (GLW), and thousand- grain weight (TGW) investigated traits, suggesting that the the relevant number of mutations in M8008. Approximately 21% of simple sequence repeat (SSR) markers showed polymorphisms between M8008 and YN15, indicating that EMS can induce a large number of mutated loci. QTL clusters (one in MY and two in MS) were detected. The QTL clusters coinciding with (MY population) or near (MS population) the marker wmc41 were associated mainly with grain-size traits, among which the the M8008 locus led to decrease in GW, factor form density (FFD), and TGW and to increase in GLW. The cluster in the wmc25-barc168 interval in the MS population was associated with yield traits, for which the M8008 locus led to decreased PH, spike number per plant ( SN), and SL.