Grain weight, an essential yield component, is under strong genetic control and markedly influenced by cultivation conditions.Here, by genome wide association analysis, 37 loci were found to exhibit significant associations with thousand grain weight (TGW) under one or more cultivation conditions.Five loci were stably associated with TGW under all four conditions examined.Their elite alleles had positive effects on TGW.Four, two, three and two loci were consistently associate with TGW under IF (irrigated and fertilized), RF (rainfed), RN (reduced nitrogen application), and RP (reduced phosphorus application) conditions, respectively.The elite alleles of IF specific loci enhanced TGW under well resourced condition, whereas those of RF, RN or RP specific loci conferred tolerance to TGW decrease when water, nitrogen or phosphorus were reduced.Four loci were constantly associated with TGW in specific experimental locations, one of which was shown to contribute significantly to TGW difference between the two experimental sites.Further analysis of 14 associated loci revealed that nine affected both grain length and width.The remaining five influenced either length or width of the grains.The elite allele of Xpsp3152 locus was found to frequently co-segregate with the larger grain haplotype of TaGW2-6A, indicating genetic and functional linkages between Xpsp3152 and GW2 important for grain weight control in cereal plants.Our work generated new knowledge on the genomic loci and mechanism underlying grain weight control in common wheat.The implications of our findings on further improving wheat grain weight trait for efficient utilization of water and fertilizer resources are discussed.