To evaluate the effect of Hydrangea serrata Seringe extract on kakdoogi(Korean radish kimchi), the kakdoogi was prepared, after supplementation, with Hydrangea serrata Seringe extract(0, 1.25, 2.5 and 5%(v/w)). The quality characteristics of the kakdoogi were investigated during 7 days of fermentation at $20^{circ}C$. The proximate components of the Hydrangea serrata Seringe leaves were 3.48% crude protein, 6.45% crude lipid, 7.98% crude fiber and 9.32% crude ash. The pH values in the samples with the extract were higher than that of both the control group and the sugar group. The total acidity levels in the sugar group was higher than that of other groups. The sugar group showed higher L value(lightness) than that of kakdoogi fermented with the extract. A value(redness) and B value(yellowness) of the supplemented kakdoogi was lower than that of the control and the sugar group on day 7. The hardness of samples with the extract was higher than that of the sugar group. And the hardness of the groups with the extract was not reduced during the fermentation period. The control group showed higher salinity than the other groups by day 4. The samples with the extract were sweeter than the control group on day 0 then the difference disappeared after day 2. Sourness of all the groups increased during the fermentation period. However the extract did not affect the hardness or overall acceptability of the kakdoogi during fermentation.