To enhance solubility and dispersibility of nutritional elements of barley grass for rehabilitation therapy, high-energy ball-milling was conducted to obtain nano-scale powder of barley grass. Ball-millings were performed at a temperature of <10 degrees C for 2, 4, 6, and 8 h respectively without N-2 protection, while an additional ball-milling process was added for 8 h with N-2 protection at the same temperature. After these ball-millings, properties of color, flavonoid, chlorophyll, flow ability, particle size, density, dietary fiber and hydration of barley grass powder were measured. As nano-scale powder of barley grass was obtained after 8 h, contents of flavonoid and chlorophyll without N-2 protection were 321 g/kg and 14.23 g/kg, respectively; that with N2 protection were 534 g/kg and 19.64 g/kg. From start to 6 h, contents of flavonoid and chlorophyll, flowability and hydration decreased; yet bulk density and tapped density increased. Soluble dietary fiber content of nano-scale powder was elevated at 164 g/kg and TDF of nano-scale powder was 290 g/kg. Reverse trend of flowabilty and hydration occurred in nano-scale powder; and lightness and colors maintained well. Nano-scale barley grass powder manifests a fascinating performance of quality, hydration and nutritional properties. Ball-milling is a processing to make barley grass easy digestion for human body. (C) 2018 Elsevier B.V. All rights reserved.