When small powered rotary rigs drill in mudstone，shale and big particle gravel with a diameter of 1,500mm for bored piles, the conventional inserted rock screw bits often present themselves slow penetration or even no penetration due to the rig's small power and small WOB. Through analyses on these problems occurred during bored pile construction for new plant building of Wanxi Pharmacy Limited Company in Xixia County, Henan, pertinent improvement measures were put forward and the good results were got.