The content of four kinds of polyphenolic extract and the variations in their antioxidant activities during germination were investigated in Ganbei 4 barley. The antioxidant activity was evaluated based on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, and ferric reducing activity. Simultaneously, the contents of monomeric phenolic acids from the crude polyphenolic extracts (four types) were determined by high-performance liquid chromatography (HPLC). The results of these analyses revealed the significant influence of malting on the content and types of crude polyphenolic extracts and monomeric phenolic acid, as well as on their antioxidant activities. The proportion of free phenolic acids was observed to be the highest in raw barley than that in germination process.. These values showed a significant decrease during the steeping process; subsequently, the values showed a remarkable increase during the late stage of germination. Correlation analysis revealed a close relation between the ferric-reducing ability, DPPH and ABTS radical scavenging abilities of the four crude polyphenols and their compositions. Monomeric phenolic acids, which were closely related to crude polyphenols, were also observed to significantly affect the antioxidant activities of crude polyphenols. Ferulic acid, catechin, and p-coumaric acid were identified as the major active phenolic acid components of Ganbei 4 barley.