Objective : This study is designed to assess the effects of Gongjin-dan on cognitive decline of the patients with mild Dementia of Alzheimer Type(DAT). Method : 33 patients with mild DAT were measured by using K-DRS, and after 100 days again. During 100 days the patients with mild DAT were treated with Gongjin-dan. The scores of K-DRS between before and after treatment were analyzed by paired t-Test. Result : 1. the mean age of patients was $70.3{pm}4.1$ years (range 65 to 84 years) 2. the mean education of patients was $5.5{pm}5.3$ years 3. the mean K-DRS score of the patients before treatment was $93.2{pm}12.1$, and the mean K-DRS score of the patients after treatment was $114.7{pm}14.5$. K-DRS scores after treatment was significantly different with the K-DRS scores before treatment.(t=9.907, r=.573, p<.00l) Conclusion : Treatment with Gongjin-dan for 100 days increased the cognitive ability in patients with mild DAT