To further identify the dominant pollutant of PVDF UF membrane, the secondary wastewater effluent organic matters were isolated into strongly hydrophobic acids, weakly hydrophobic acids and hydrophilic matter by DAX-8／XAD-4 synthetic resins and then the filtration tests were conducted with each constituent. The membrane-foulant and foulant-foulant interaction forces were measured with homemade PVDF micro-particle probes and the corresponding foulant-coated probes respectively with atomic force microscopy, as well as membrane morphology. The results showed that the microscopic force could effectively predict membrane fouling behavior. Adhesion between hydrophilic matter and PVDF membrane was the biggest, whereas adhesion between weakly hydrophobic acids and PVDF membrane was the smallest. The membrane-foulant force was bigger than the foulant-foulant force, illustrating that membrane-foulant force was the key factor to control the fouling behavior of PVDF UF membrane, and an effective mean to control PVDF UF membrane fouling was to reduce the force between the hydrophilic matter and PVDF membrane.