In this research, we mainly studied the effects of partially hydrolyzed polyacrylamide (PHPAM) on crude oil interfacial properties; this is important in studying the stabilization mechanism of produced fluids with polymer and oil/water separation. The crude oil was separated into amphoteric, acidic, basic, and neutral fractions by ion-exchange chromatography. The molecular weight of the amphoteric fraction was the highest, and the acid number of the acidic fraction was the biggest. Fourier transform infrared spectroscopy and elemental analysis of the functional fractions of Gudao crude oil showed that sulfur-, nitrogen-, and oxygen-containing functional groups occur mainly in the amphoteric, acidic, and basic fractions. The molecular weight and concentration of PHPAM had significant influences on the dilational moduli, dilational elasticities, and dilational viscosities of the crude oil and its fractions. As the molecular weight of PHPAM increased, the dilational moduli, elasticities, and viscosities of the oil-PHPAM/water solution interfacial films of crude oil and its acidic/basic fractions first increased and then decreased. The values were highest and the interfacial films were most stable when the PHPAM molecular weight was 7.6 X 10(6) g mol(-1). As the concentration of PHPAM increased, the dilational moduli of the oil-PHPAM/water solution interfacial films of the Gudao crude and its fractions consistently increased. The higher the concentration of PHPAM in the water solution, the more stable the oil/water interfacial film. As the dilational frequency increased, the dilational moduli, dilational elasticities, and phase angles of the oil/water interfacial films of the Gudao crude oil and its fractions increased but the dilational viscosities decreased.