Abstract: The rheology control is a key technical problem in the high density drilling fluid operation. Through conducting research on the classification of high density drilling fluid, the optimal grain distribution of adulterant is determined using the density-grain-viscosity curve. By conducting research on the optimization of the preparation process of basic mud, the drilling fluid system of strong inhibition, the grain distribution of adulterant and drilling fluid, applying ultra-micro and sub-micro particle stabilizing technique, intensifying solid control, systematic high density cationic drilling fluid technologies are developed. They have been applied to the Jiudong Oilfield. It is indicated that the viscosity of the drilling fluid with its density ranging from 1.95g/cm3 to 2.20 g/cm3 can be regulated from 55 s to 180 s, when the n is less than 0.7 and the K is less than 0.9. The ratio of dynamic shear force value to plastic viscosity is between 0.4 and 0.8, and the Kf is less than 0.1. The rheology and lubricity is better controlled, as well as the sticking less occurs. It enables the Chang-31 well to realize no drilling accidents.