The invention relates to a drilling fluid rheological parameter control method meeting a power law mode. A reasonable dereferencing range of a rheological parameter is determined according to a well bore size, a borehole diameter expansion rate, an annular clearance, solid phase particles and a mud pump output volume, indications of drilling fluid under different rotating speeds are measured and converted into corresponding shearing rate and shearing stress, the rheological parameter is estimated, and an on-site small test is performed according to whether the estimated value is in the determined dereferencing range so as to determine the adjustment measures of the drilling fluid. In the method disclosed by the invention, a plurality of factors are considered to set the reasonable dereferencing range of the rheological parameter, reasonable judgment is made on the adjustment of the drilling fluid through improving the estimation precision of the rheological parameter, the maintenance measures of the drilling fluid are determined by the on-side small test, the dosage of treatment agents is saved, and the drilling cost is reduced.