HA and FA composition and binding characteristics of soil combined humus differentiated by the modified Hseung's method were studied. The results obtained are summarized as follows: 1.It was observed that with the rise of soil pH, there was a tendency to increase the loosely combined humus(H₁) extracted with 0.1mol/L NaOH from soil and to decrease the stably combined humus(H₂) extracted sequentially by a 0.1mol/L NaOH-0.1mol/L Na₄P₂O₇ mixture from the residues. Statistical analysis showed that H₁ was very significantly positively correlated to free Fe and Al but negatively to exchangable Ca, and that H₂ was significantly positively correlated to exchangable Ca but negatively to free Fe and Al. No significant correlation was found between tightly combined humus(H₃) and pH or various binding materials of soil. 2. The ratio of humic acid to fulvic acid (HA/FA) was lower in H₁ than in Hz. The former was positively correlated with free A1 and the latter positively with pH and exchangable Ca of soil.3. Elemental analysis results of the extracting solution indicated that H, was actually Al/Fe-combined humus with less Ca-combined humus, and H₂ was mainly Ca-combined humus.