Abstract: The geology of Halfaya Oilfield is complicated and there tends to be problems such as bit balling, creepage hole shrinkage, pollution of high density drilling fluid by high concentration Ca2+ during the drilling. The difficulties in maintenance of drilling fluid are inhibition of soft mudstone distribution, stabilization of pH value and elimination of Ca2+. Through selection and optimization of treating agent of drilling fluid, BZ-HIB and BZ-DCA are introduced and technical measures are improved to solve the problems with control of rheological property of high density mud, stabilization of pH value, and elimination of Ca2+. It has significant effects on increase of drilling rate and reduction of difficulty in maintenance.