Our company undertakes one oil shale exploration project of the Shell Companies in Jilin; this is the first time to get in the oildrilling filed from geologic core drilling for our company.The main rocks in this mining area are mudstone, sandstone, shale and clay rock. They are uneven thickness, changing frequently, soft and strong water senstivity. The key for successfully drilling is mud system and performance. After failed drilling No.1 and No.2 well of Dunhua, we developed a potassium salt / polymer drilling fluid, and applied to the Jilin Yitong, Nonga mining area and finished about 2375 meters. In the process of drilling, the well wall is stability, no drilling burying accident. We got higher drilling efficiency and better engineering quality.