Subcritical water extraction is one of the green ways to isolate plants biomass components. In this work, it has been applied as a media to extract beta-glucan from barley (Hordeum vulgare L). The extractions were carried out at temperatures of 130-170 degrees C and a pressures of 10-40 MPa, using a semi-batch system. UV-vis spectra of liquid fraction products showed a high content of hemicelluloses, including glucan compounds. Results of FT-IR spectra analysis showed that beta-glucan has been extracted from barley grains after subcritical water treatment. The elemental analysis showed that dehydration and decarboxylation occurred during subcritical water extraction of barley grains at these conditions. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of water-soluble products were approximately 500 Da to 1167 kDa. To improve the extraction process, the CO2 was added. At the same extraction time, the yield of beta-glucan in the liquid fraction products increased clearly with the presence of CO2. (C) 2015 Elsevier B.V. All rights reserved.