The failure of conventional drilling fluid system and multiple complex situations caused by deep reservoir with high temperature in Dingbei block, it is necessary to develop a set of drilling fluid with high temperature tolerance. Through analyzing the essentials of well drilling incident and the properties of potassium ammonium based drilling fluid, it is clear that the drilling fluid should be improved in high temperature inhibition, stability, filtration reduction and sealing ability. A lot of high-temperature drilling treatment agents have been tested in rheology, filtration, sealing and lubrication, SMC and SPHN are chosen as anti high temperature flirtation reducer, KCl and polyamine as anti high temperature inhibitor, HQ-10 as anti high temperature plugging agent, white oil and graphite as lubricant, SF-1 as anti high temperature diluent; the appropriate bentonite content is determined to be 4%, the high temperature drilling fluid system formula is finally obtained. The laboratory evaluation experiment shows that the viscosity, shear and water loss of this high temperature drilling fluid can still meet the design requirements after 180℃ hot rolling for 72h and anti-contamination of NaCl and CaCl2 are 10% and 4% respectively, the permeability recovery rate of damaged reservoir core can reach more than 80%. This high temperature drilling fluid formula will provide support to safe and effective drilling in Dingbei block.