Kojongsi persimmon (Diospyros kaki) is the major cultivar of astringent persimmon in southern of Korea. Kojongsi persimmon leaf has been traditionally used for acute and chronic diseases in Oriental countries. The purpose of this study was undertaken to investigate the antioxidative activities of the extract of Kojongsi persimmon leaf during growth. We investigated the antioxidant effects of the persimmon leaf extracts during growth on total polyphenol, total flavonoid, electronic donating ability (DPPH), nitrite (NO) scavenging and superoxide dismutase (SOD)-like activity. The next, we investigated the possible cell protective effects of the persimmon extract treatment against ultraviolet B (UVB)-induced injury in HaCaT keratinocytes. The contents of total polyphenol and flavonoid in leaf extract of Kojongsi persimmon were increased in time-dependent manner. In Jun, DPPH and NO radical scavenging and SOD-like activities in the leaf extract of Kojongsi persimmon was increased to the highest. However, the antioxidant activities in persimmon varieties were not any difference. The cell cytotoxicity by UVB irradation in HaCaT keratinocytes was significantly increased with the compared to the control group. However, the treatment of leaf extract of Kojongsi persimmon in HaCaT keratinocytes was shown to protective effect against UVB-induced cell cytotoxicity. These results suggest that the leaf extract of Kojongsi persimmon has potent antioxidant activity, and protective effect against UVB-induced keratinocyte injury. Thus, these properties may be contributed in the care of acute and chronic diseases.