This study was aimed at determining the contents of different forms of polyphenols and antioxidant activities of hulless barley. The contents and types of polyphenols were detected by Folin-ciocalteu and HPLC, respectively. The antioxidant activity was investigated by testing the scavenging ability of DPPH radicals. Results showed that the free, bind and total phenolic content of hulless barley decreased respectively by 89.3%, 23.7% and 52.7%, and esterified polyphenols slightly increased by 2.49 mg/100 g after processing. The variety of polyphenols segregated from free polyphenol extracts increased three. Besides, 7 phenolic compounds were all tested in bind polyphenols. Ferulic acid had the highest content mainly existing in bound state. Simultaneously, its content significantly increased after extrusion process. Under the control of these two conditions, antioxidant activities were 1.76 mg/g and 0.93 mg/g, respectively. Moreover, a strong positive correlation between polyphenol and antioxidant activity was found. It could be concluded that extrusion process could change the texture and taste of hulless barley, while the polyphenol content and its antioxidant activity were reduced.