The invention discloses a high oil-water ratiooil base drilling fluid system. The system is prepared from, by volume, 90-95 parts of base oil and 5-10 parts of an aqueous phase, and further comprisesa primary emulsifier, an auxiliary emulsifier, a wetting agent, organic soil, calcium oxide, an emulsifying sealing material, a keritesealing material and calcium chloride brine, wherein the weight ofthe primary emulsifieris equal to 0.8-1.8% of the overall weight of the base oil and the aqueous phase, the auxiliary emulsifier1.0-2.0%, the wetting agent 1.2-1.5%, the organic soil 2.0-3.0%, the calcium oxide 3.0-4.0%, the emulsifying sealing material 3.5-4.5%, the keritesealing material 1-1.5% and the calcium chloride brine 2.0-2.5%. The high oil-water ratiooil base drilling fluid system is low in ECD value, has good emulsion stability, low rheological property and good well wall flushing capability, facilitates borehole cleaning, cost saving of drilling fluid and maintenance of on-site performanceof the drilling fluid, effectively reduces the risk of well leakage, and can avoid rheological propertyrise caused by drilling a stratum in which the moisture content is high.