This study was carried out to investigate ginsenoside content in different root parts and the correlation between root diameter and ginsenoside composition of Panax ginseng C. A. Meyer cultivated by direct seeding. The unit contents of ginsenoside were 29.65, 28.76, 26.34 mg/g, respectively in 4, 5, 6 years old. However, the total contents of ginsenoside were 431.97, 606.56, 657.80 mg/root, respectively. Total ginsenoside content of fine root was higher than that of main root and lateral root. These tendencies were related to decrease by the increase of root diameter. When diameter of main root and lateral root were the same in different ages, the total ginsenoside content was higher in the order of 4 > 5 > 6 years old roots. Except for ginsenoside-Rg1, other ginsenosides components (PD/PT and total ginsenosides) had highly negative correlation with the root diameter within whole root, main root, lateral root and fine root, which indicated that ginsenoside content is correlated to root diameter. As results, it is suggested that ginsenoside content can be predicted.