In this study, 45 KCl/polymer type of drilling fluid samples were prepared for statistical analysis. Six difference (600, 300, 200, 100, 6, and 3) readings at standard Fann viscometer speeds were determined in order to estimate the rheological model parameters of our different models, as follows: Bingham Plastic, Power-Law, Hershel-Bulkley, and Robertson-Stiff. Parameters of the rheological models are estimated by explicitly solving the required number of equations simultaneously. Different statistical techniques (variance, standard deviation, coefficient of variation, mean and sum square error, skew, mean and median) were used in order to see how calculated shear stress values (via four different rheological models) are closed to the observed values. It was observed that the Power-Law model best describes the KCl/polymer type of drilling fluid samples.