A water-based drilling fluid, GreenLube, was produced through O/W emulsion with 33% vegetable oil, 50%~80% polyols aqueous solution and compounded surfactant (sorbitan trioleate and polyoxyethylenesorbitan monooleate, HLB=6~7). GreenLube was a readily biodegradable and low toxicity material with 0.95 BOD5/COD and 35981 mg/L 96 h LC50. Compared with based slurry, GreenLube (30 kg/m₃) could reduce the torque value for fresh water and sea water based bentonite by 69% and 47%, respectively. The properties of GreenLube were further evaluated by JFC, PEM and PEC drilling fluid systems currently used in offshore oilfield. The results showed that the lubrication factor for test systems were reduced from 0.24—0.26 to 0.14—0.16 without influence of the mud rheologies. GreenLube had been successfully used in several wells of Bohai oilfield. The friction coefficient of mud cake and torque of drilling tool were notably reduced.