Abstract: The importance and difficulties of the application of high-density drilling fluid in ultra-deep wells in the outside district of the Tahe Oil Field were discussed from the aspect of petroleum engineering. Combined with current implement situations, we made several methods on dealing with drilling fluids which are in HTHP well-bore surroundings. Through series of control-experiments, we imitated the true surroundings down hole via a roller oven. We optimized the handling ways to fluids from gained parameters according to the experiments. The keys of successfully manipulating deep well high-density fluids are bentonite, solid phase, filtration control, system's rejection capability and stability.