This study was conducted to improve preparations of oriental drugs by enzyme. Total sugar, reduced sugar, hydrolysis rate, and amylose content were compared in Korean yam starch and some oriental drugs treated different enzyme levels and treatment times. The results were as follows. Reduced sugar and hydrolysis rate by enzyme of yam starch were significantly increased according to increments of enzyme level and treatment time. Amylose content in yam starch was significantly decreased to increment of enzyme level and treatment time. Total sugar content in some oriental drugs of Sangmaeksan, Yukmigiwhang, Yukshinsan, Manbungsarungsan, and Sanyaksogalum were 46.08, 44.87, 11.15, 10.67, and $6.l6mg/m{ell}$, respectively. There was no significant difference in hydrolysis rate by enzyme of Sangmaeksan, Yukmigiwhang, Manbungsarungsan. However, hydrolysis rates of Yukshinsan and Sanyaksogalum were significantly highest in 0.2% enzyme and 0.5% enzyme groups, respectively.