Due to the development of mud shale, carbonaceous mudstone and oil shale in some sections of Luopangyuan block in Yanchang oilfield, the directional backpressure, block falling and serious strata collapse often occur in the drilling construction, the research on anticollapse drilling fluid system for this block is carried out. The results show that 4% KCl, 5% polyalcohol and 0.6%～0.8% SI-150 can be used as inhibitory anticollapsing agent, and 1% oxidized asphalt, 3% superfine calcium carbonate (1% 2000 mesh + 2% 3000 mesh) and 1% elastic graphite as plugging anticollapse treatment agent to help prevent collapse, together forming an anticollapse drilling fluid system suitable for Luopangyuan block in Yanchang oilfield. With the good sealing property and inhibition of this drilling fluid system, the shale rolling recovery was remained at over 93%, extreme pressure lubrication coefficient controlled less than 0.07. The drilling fluid system has been successfully applied in 2 horizontal wells of Luoping 16th well and Puping 48th well with good results.