In order to satisfy the increasingly stringent requirements for environmental protection，the biological toxicity and degradability of several emulsifiers， internal phase salts and base fluids were tested， and then an environment-friendly non-water-based drilling fluid system was constructed on the basis of plant oleic acid and its ester derivative BIO-EMUL and BIO-COAT，combining with base fluid BIO-OIL and sodium acetate solution by measuring the electrical stability，emulsifying efficiency of water-in oil emulsion and oil/water interfacial tension，interfacial rheology between BIO-EMUL+BIO-COAT solutions and BIO-OIL. The fundamental performance and anti-contamination ability of the drilling fluid was evaluation. The results showed that BIO-EMUL and BIO-COAT could effectively reduce the interfacial tension of oil/water and form water-in-oil emulsions with demulsification voltage up to 350 V and emulsifying efficiency up to 95%. The LC₅₀ of the water-in-oil emulsion system was about 28 200 mg/L，and the BOD₅/COD_Cr was greater than 0.25，indicating that it was an environment-friendly system with low biological toxicity and good degradability. The prepared drilling fluid system had a wide range of applicable density and strong anti-contamiation ability，which provided a foundation for the future study of environmental protection non-water-based drilling fluid system and materials.