Nano-SiO2 was organically modified with silane coupling agent-KH570 to prepare the modified Nano-SiO2 oil dispersion system. By increasing the dosage of KH570, the ζ-potential (absolute value) and the char yield values decreased gradually. When KH570 was 5%, the maximum contact angle with water reached 79.8°. Then, the modified Nano-SiO2 was composed with petroleum sulfonate (PS) and its ability of reducing the O/W interfacial tension was measured. The results showed that, O/W interfacial tension reduced to about 5.86×10-3 mN/m when the Nano-SiO2 and petroleum sulfonate composite was mixed with the mass fraction of 0.2:0.3%. The emulsion stability coefficient was 2.15 after 120 min which was the minimum. It indicated that this compounded system had the best emulsifying ability because Nano-SiO2 particles were dragged onto the O/W interface by the PS molecules to improve the intensity of O/W interface.