A humic acid extracted from dark brown soil was fractionated by the fractional precipitation technique into 12 fractions which were characterized by various methods. Results showed that with the increase of alcohol concentration, the degree of humification and molecular weight of humic acid fractions thus obtained showed a tendency to decrease gradually, total N, the relative contents of total hydrolyzable N and amino acid N increased progressively but the amino sugar N and NH₄⁺-N decreased. The possible reason for causing the difference between the results got by this method and the gel filtration method is discussed.