This study investigated the effects of soluble organic matters on membrane fouling characteristics, using silt density index (SDI) and modified fouling index (MFI) to evaluate the fouling potential. Experimental results demonstrated that humic acid had significant effects on membrane fouling indexes. When its concentration was in the range of 0.01-0.05 mg/L, the SDI(15) and MFI were 2.9-3.9 and 5.4-13.8 s/L(2), respectively. According to the linear equations of MFI measurements, the fouling potential was in the order of humic acid > nucleic acid - protein > glucose. Moreover, the molecular weight of dextran played an important role in membrane fouling indexes. Furthermore, a mathematical analysis of filtration experiments based on Saturation curve was developed in this study. The maximum accumulated filtrate (V,.) and the constant of filtration (k(f)) could be obtained to improve the precision of membrane fouling prediction. (C) 2008 Elsevier Ltd. All rights reserved.