Barley(Hordeum vulgare L.) is one of the oldest domesticated crops, showing dramatic adaptation to various climate and environmental conditions. As a major cereal crop, barley ranks the 4th after wheat, maize and rice in terms of planting area and production all over the world. Due to its diploid nature, the cultivated barley is considered as an ideal model to study the polyploid wheat and other Triticeae species. Here, we reviewed the development, optimization, and application of transgenic approaches in barley. The most efficient and robust genetic transformation has been built on the Agrobacterium-mediated transfer in conjunction with the immature embryo-based regeneration. We then discussed future considerations of using more practical technologies in barley transformation, such as the T-DNA/transposon tagging and the genome editing. As a cereal crop amenable to genetic transformation, barley will serve as the most valuable carrier for global functional genomics in Triticeae and is becoming the most practical model for generating value-added products. Barley (Hordeum vulgare L.) is one of the oldest domesticated crops, showing dramatic adaptation to various climate and environmental conditions. As a major cereal crop, barley ranks the 4th after wheat, maize and rice in terms of planting area and production all over the world. Due to its diploid nature, the cultivated barley is considered as an ideal model to study the polyploid wheat and other Triticeae species. Here, we reviewed the development, optimization, and application of transgenic approaches in barley. The most efficient and robust genetic transformation has been built on the Agrobacterium-mediated transfer in conjunction with the immature embryo-based regeneration. We then discussed future considerations of using more practical technologies in barley transformation, such as the T-DNA / transposon tagging and the genome editing. As a cereal crop amenable to genetic transformation, barley will serve as the most valuable carrier for global functional genomics in Triticeae and is becoming the most practical model for generating value-added products.