The invention discloses a high-stability step gauge and a preparation method thereof, wherein the step gauge is provided with a base body; the base body comprises a pillar carrier arranged along one coordinate direction; gauge block installing blocks are distributed and configured on the pillar carrier, and measuring pieces are fixedly installed on the gauge block installing pieces. The high-stability step gauge is good in precision stability, small in dimension and powerful in function; through reasonable combination of the base body and the gauge block installing blocks, the shape change bias of the step gauge caused by self-weight of the base body and other factors is effectively and significantly reduced; material use and step gauge weight are reduced according to the minimized design of the base body specification; thus the high-stability and high-precision calibration entity are provided. Through taking a cylindrical rigid supporting body as the base body, the preparation provides the stable and low shape change performance on length direction; the suit gauge block installing blocks are high in stability of fixedly installation, and accurate in positioning assembly of the measuring pieces.