Abstract: JGN-A weighting drilling fluid system used in Daqing oil field has a series of problem:poor stability, rapid increase of viscosity and shear and improper dynamic/plastic viscosity ratio. The application of new weighting material-activated barite instead of conventional barite in drilling fluid has solved the problem existed in JGN-A heavy drilling fluid as well as saved the usage of weighting material. water and additive and reduced the discharge of heavy drilling fluid. This paper presents the basic mechanism of activated barite, lab evaluation and field test and concludes that the activated barite has a bright future in application and is valuable for further wide application.