In order to ensure better conservation and to increase the nutritive value of barley straw, the effects of lactic acid bacteria (LAB) and cellulase addition were studied. Two cellulases were Acremonium cellulase (AC) and Meiji cellulase (MC). Both cellulase and LAB addition decreased the pH values (P < 0.05) and increased lactic acid content when compared with the control, and their combination had further benefits over them alone. The efficiencies of improving fermentation quality were AC + LAB > MC + LAB > AC > MC > LAB. Cellulase addition significantly reduced ADF and crude fiber contents, and increased NFE content compared to the control (P < 0.05). The TDN contents of barley straw silages treated with AC, AC+LAB, MC and MC+LAB were increased by 11.9%, 15.5%, 7.0% and 10.8%, respectively.