The invention relates to a method for online setting the speed range and the speed accuracy of a turntable based on inertial guidance testing. The method comprises dividing the subdivision multiple of a turntable photoelectric encoder into shifts according to a speed range and speed accuracy requirement; and controlling a computer through the turntable to online switch the subdivision multiple of a subdivision circuit in order to achieve a large rotating speed range and high-low speed accuracy of the turntable. The method provides an accurate basis for the online switching of the speed range and the speed accuracy of the turntable by reasonably setting the low subdivision multiple of the turntable, the high subdivision multiple of the turntable, and the maximum operating rotating speed under the high subdivision multiple, and performs an inertial guidance test by setting a reasonable speed range on this basis so as to satisfy a high rotating speed range and guarantee high speed accuracy. The testing in all speed ranges is completed in a test when the turntable is not changed, thereby saving resources and devices.