Abstract: The volatile oil from brewer 's spent grain was extracted by water- steam distillation and the chemical components were determined by GC-MS.The relative contents of the chemical components were determined with peak area normalization method. Thirty- eight compounds, which occupied 91.09% of total constituents were identified.The major constituents were identified as palmitic acid ( 48.90%) , linoleic acid ( 26.10%) , myristic acid ( 3.02%) , stearic acid ( 2.74%) , furfural ( 1.47%) , phenylacetaldehyde ( 0.94%) .The scavenging capacity against DPPH free radical of volatile oil from brewer's spent grain was determined by spectrophotometry. The volatile oil ( 25%) exhibited significant scavenging capacity against DPPH free radical in a concentration-dependent fashion with the IC50 value of 50.53μL.