Interfacial dilatational rheology of the interface between ORS-41 surfactant solution and Zhuangxi crude oil was investigated by small periodic oscillation method at 55°C using DSA100 interfacial dilatational rheometer. The influence of experiment conditions and surfactant on interface properties was studied by measuring the parameters of interfacial dilatational modulus, interfacial elastic modulus and interfacial viscous modulus. The results showed that the droplet size and amplitude had slight influence on the experiment results. The main relaxation process which occurred on the interface was diffusion relaxation. Dilatational modulus, elastic modulus and viscous modulus increased with increasing oscillation frequency. The appropriate experiment condition was obtained as follows: 0.01% mass fraction of ORS-41, 1 μL amplitude of oil drop, 10 s oscillation period and 300 s equilibrium time of surfactant. The interfacial film could be seen as elastic film without ORS-41, and elastic modulus and dilatational modulus was 2.8409 mN/m and 2.8490 mN/m respectively, while viscous modulus was approximately zero. Dilatational modulus and elastic modulus of the interface film decreased sharply to 0.1503 mN/m and 0.1786 mN/m after adding ORS-41, but viscous modulus increased at first then decreased.