Formation damage is prone to occur during drilling into the formations with medium/high permeability in Jabung Oilfield, Indonesia. To prevent formation damage and enhance productivity of oil wells, a novel low-damage drilling fluid was developed on the basis of the modification of currently used KCl polymer drilling fluid using a special technology. By virtue of the synergistic effect of ideal packing agents and film-forming agents, a sealing layer with high pressure bearing capability can be formed on the rock surface of borehole, so as to prevent drilling fluids from invading into formations effectively. It is shown from the results of numerous experiments that this drilling fluid has excellent rheological properties, very low filtration rates (API filtration rate<4mL and HTHP filtration rate≤12.5mL), good lubricity, and strongly inhibitive character to shale. Also, it exhibits remarkable effectiveness of formation protection indicated by the returned permeability as high as 88.11% and extremely low dynamic filtration rate lower than 4mL.