Abstract: Oil-based drilling fluids generally have various disadvantages, for example, the base oil is difficult to degrade and non-renewable. Therefore, an investigation on the renewable biosynthesis oil-based drilling fluid system was carried out. The biosynthetic base oils were synthesized by the catalytic hydrogenation and molecular isomerization of natural bio-oils and fats. Based on the biosynthetic base oil and modified organic soil, the renewable biosynthesis-based drilling fluid system was formed through adding other drilling fluid additives and the optimized dosage, and its performance was evaluated. The biosynthetic base oil was a mixture of C₁₂–C₂₄ branched isoparaffins, which had excellent safety, environmental protection and viscosity-temperature properties. The high temperature and high pressure filtration loss of the renewable biosynthesis-based drilling fluid system was lower than 12 mL, the sedimentation stability was good, the demulsification voltage was up to 768 V, and the 96 h semi-lethal concentration was greater than 1 000 000 mg/L. The biosynthetic oil was able to resist the invasion of 20% formation water and 10% inferior soil, and the rolling recovery rate of cuttings reached 98.06%; the permeability recovery rate of the contaminated cores was up to 83.5%–92.3%. The research results showed that the oil with a biosynthetic base possessed the advantages of low toxicity, environmental protection, degradability and regenerability. The prepared drilling fluid exhibited good properties in emulsion stability, anti-pollution, lubrication, inhibition, reservoir protection, safety and environmental protection, which fully met the needs of drilling fluids under complex geological conditions.