Due to the problems of traditional W/O emulsion drilling fluid, such as high viscosity, low gel and worse cuttings carrying capacity under high temperature, a new 200℃-resistance W/O emulsifier was designed and synthesized. A new W/O emulsion drilling fluid system with low viscosity and high gel was obtained after optimizing various agents, and the formula was: 90:10 oil-water ratio, 6.5% primary emulsifier DQGC-II, 2.2% secondary emulsifier DQNS-II, 4% No.4 organic clay, 1.5% CaO and 6% fluid loss control DQHA. This system showed good characteristics in lab including high electricity stability（ES1644V）, heat stability, good rheology, especially appropriate viscosity and gel under a low speed with 19mPa·s PV, 8 Pa YP, 0.42 YP/PV, 8.6mL HTHP filter loss. The new drilling fluid system was applied in GS-3 well of Daqing oilfield, there was no downhole complex. The ratio of overcut in average was 5.83%, and the following construction went smoothly. This new W/O drilling fluid system could replace the VersaClean system of M-I SWACO.