Geothermal Well GYx in Gaoyang Geothermal Field was a three-section well with a completion depth of 3920m. Neogene and Paleogene formation was drilled in this well, and the target layer was Wumishan Group of Jixian System. Drilling operations in the formation was difficult due to many problems such as sticking, leakage, chipping, collapsing, and even occurrence of oil and gas layers. Preparation of proper drilling fluids were very critical and difficult, especially for the second section drilling. Polymer mud with the macromolecule coating agent and silica-based anti-collapsed mud with high temperature resistance were adopted for the drilling fluid, and the high temperature-resistant drilling material was used. The density of the drilling fluid was controlled according to the formation pressure. The shale inhibitor was used to prevent shale hydration and swelling, and to control the water loss of the drilling fluid as well. The mud lubricity was improved by adding some lubricating agent. The four stage solid control equipment was used to clean the drilling fluid. By taking these measures, the drilling fluid adopted in Well GYx provided good performance, which had eliminated the drilling risks; meanwhile the penetration rate was greatly improved.