Abstract: Currently,evaluating bentonite used for drilling fluid is complicated because it may involve a large number of testing items,and an arduous process of testing and evaluation,where the evaluation period is long and the workload heavy.Most relevant standards focus on the properties of bentonite at room temperature,but we still lack methods that optimize bentonite used for high temperature and high density drilling fluid.To solve these problems,a method for optimizing bentonite based on a characteristic diamond diagram was proposed. It is based on analyzing the internal relations between performance parameters such as quality and yield of bentonite,rheological property and filter loss of bentonite slurry.In this method,the influence of temperature on the properties of bentonite was taken into account.Researchers tested the yield of bentonite and the plastic viscosity,yield point and filter loss of bentonite slurry before and after aging.After completing those calculations,the relational expression between the dosage of bentonite and plastic viscosity,yield point and filter loss was determined.The next step involved calculations to determine the quality of the bentonite.Those calculations involved comparing the projected performance parameters with those of reference bentonite and and then drawing the characteristic rhombus to calculate the quality value of bentonite.Quality values of five bentonite samples were calculated and sorted in order;the quality of five bentonite samples was then matched with the performance of the corresponding drilling fluid.Consquently,this indicates that the optimizing method for drilling fluid with bentonite is reliable by the characteristic diamond diagram.