The reasonable selection for drilling fluid rheological model and the precise calculation for rheological parameters is the preconditions for optimizing drilling fluid design. After comparison between five drilling fluid rheological models which are currently normally used, the regular calculation methods for rheological parameters were analyzed and their insufficiencies were point out. The rheological parameters under five models were data processed with regression analyses. Some calculation software was developed out. Comparison between and analyses of two calculation methods for rheological parameters were made. The advancement and veracity of linear regression were shown out. Optimization of rheological models was realized through calculation of rheological parameters by computer software and output of rheological curves for respective models.