To increase the shelf-life of strawberry, samples were treated with two gel packs containing slow-released chlorine dioxide (ClO2) gas at 3~5 ppm for 6 days at room temperature and the changes in the major chemical components (ascorbic acid, polyphenols, flavonoids and anthocyanin) contents and antioxidative activities (DPPH, ABTS radical scavenging and metal chelating activity) were investigated. The content of ascorbic acid of control was 40.38 mg% and contained 35.67~44.75 mg% during 6 days. There was no tendency to increase or decrease during storage period. The contents of ascorbic acid of control and 3~5 ppm ClO2 gas treated samples were not significantly different during storage period. The content of polyphenol compounds of initial stage was 111.23 mg% and contained 117.78~132.40 mg% during 6 days. The contents of polyphenol compounds of 3~5 ppm ClO2 gas treated samples were 103.51~130.25 mg%. There were no significant different between them during storage. The flavonoids and anthocyanin contents were not different from the control during storage period regardless of 3~5 ppm ClO2 gas treatment. Furthermore, antioxidative activities were not different among the control and ClO2 gas treatments during storage.