Background <p>Sorghum is the key grain for brewing distilled liquors. Grain composition, particularly tannin and starch levels, is closely linked to the sensory characteristics and yield of the final product. Developing elite sorghum cultivars with suitable tannin and elevated starch content is thus essential for producing liquors with diverse and distinct aroma profiles. Investigating the natural variations of grain composition in sorghum germplasms and identifying underlying genetic loci can facilitate the improvement of sorghum’s nutritional value.</p> Results <p>This study established near-infrared reflectance spectrometer (NIRS) non-destructive calibration models for determining sorghum tannin and starch contents based on phenotypic identification of 214 representative sorghum cultivars. A genome-wide association study (GWAS) of tannin and starch contents was performed based on two years and two locations of phenotypic data. A total of 18 associations with 338 single nucleotide polymorphisms (SNPs) scattered over 4 chromosomes were detected significantly associated with tannin and starch contents. Among these, two associations for tannin content and two associations for starch content were expressed in different environments, indicating that they were likely to be stable quantitative trait loci (QTLs). Through linkage disequilibrium (LD) block and haplotype analysis, a promising gene, Sobic.003G118266, which encodes chalcone synthase (CHS), was identified as orthologous to structural genes in known tannin synthesis pathways; while another promising gene, Sobic.004G353100, annotated as a glucose-6-phosphate translocator (G6PT), was determined to be a putative regulatory node in plant starch synthesis.</p> Conclusion <p>These results provided important genetic variations and candidate genes to accelerate the improvement of sorghum breeding for liquor-brewing quality related traits.</p>