Awn is a specialized extension at the tip of lemma or glume of floret in cereal species， consisting of chlorenchyma cells and vascular bundles which support photosynthesis and nutrients transport， respectively. The awn plays important roles in plant defense， photosynthesis and grain filling， as well as facilitate the threshed grains embedding in soil and the geminated seedlings come up. Cultivated barley （Hordeum vulgare L.） has awn remained post domestication， and various morphological diversifications of the awns have been observed within natural population. Studies on genetical regulation and distribution of the barley awn variants have both theoretical and practical significance. In this study， a barley mutant with hooded awn was identified and genetically attributes to a single dominant mutation. By taking use of bulked-segregants-analysis （BSA） the mutation was mapped towards the end of short arm of the barley chromosome 4H， where the barley gene HvKNOX3 resides in the interval. A local duplication of 305 bp fragments in the fourth intron of HvKNOX3 was found to co-segregate with the hooded phenotype. HvKNOX3， which encodes a homeobox protein with function in transcriptional regulation， expressed specifically in young spikelets 1~1.5 cm long at early development and the rachis of 35 days after planting. By analyzing the sequence diversity of the HvKNOX3 among 20 representative landraces/cultivars of the barley pan-genome， the coding sequences were highly conserved while the exons or untranslated regions were detected with rich amount of variations， others are located in non-coding regions. With a co-dominant marker that captures the 305 bp fragmental duplication in genotyping of 238 Chinese barley landraces， a significant high ratio of the hooded genotype was observed amongst germplasms that collected from Tibet， providing evidence for the presumption that the hooded awn variant was originated from Himalayan area.