The interfacial adsorption behavior of oil and water has great influence on emulsification stability and emulsification mechanism in oil-based drilling fluid. In this paper，the dynamic interfacial tension change and interfacial viscoelasticity of oil-based drilling fluid main emulsifier PF-BIOEMUL and oil-based drilling fluid auxiliary emulsifier PF-BIOCOAT at the oil/water interface were studied by using interfacial dilatational rheology technology，and the micro-rheology of emulsion prepared by PF-BIOEMUL and PF-BIOCOAT was also studied. The results showed that the main function of PF-BIOEMUL was to provide elastic modulus and improve the strength of oil/water interface membrane，and the optimum concentration was 2.0% . The main function of PF BIOCOAT was to provide viscous modulus and reduce the interfacial tension between oil and water，and the optimum concentration was 1.5%. PF-BIOEMUL and PF-BIOCOAT could be adsorbed on the oil/water interface at the same time， which not only ensured the composite emulsifier had low oil/water interface tension，but also had better interfacial film stability， and the formed emulsion had a three-dimensional network structure. All these studies provide theoretical basis for stability research of oil-based drilling fluid system.