The experiments were carried out to investigate the antimicrobial activity and the content of isoflavonoids each fraction of the methanol extract from Korean arrowroots. The strongest antimicrobical fraction of the methanol extract was the etylacetate fraction and the other fraction was not detected antimicrobial activity. The yield of the ethylacetate fractation was 7~9% of the methanol extract of Korean arrowroot TLC was carried out using silical gel plate and CH$_2$C1$_2$- $CH_3$OH(7 : 3) and puerarin, daizin were detected by spraying 10% H$_2$SO$_4$ and Rf was 0.60 and 0.69, respectively. Puerarin, daidzin and daidzein contents were determined of the ethylacetate fraction of the sample Puerarin and daidzin contents were abundant in the samples of November, while daidzein content was abundant in the sample of Februery.