It is one of the big bottleneck problems for graphene to be uniformly distributed in ceramic matrix composites. A two-step approach was applied to prepare Graphene Nanoplatelets/Yt tria-Stabilized Zirconia (GNPs/YSZ) composites. Initially, GNPs were combined with YSZ through nanoparticle regranulation technology to obtain uniformly dispersed powders. Subsequently, the prepared powders were sintered by Spark Plasma Sintering (SPS). Systematic investigation was carried out to examine how GNPs regulate the phase, microstructures, and nanomechanical properties of GNPs/YSZ composite ceramics with different sintering temperatures. Results show that the GNPs can inhibit the coalescence of adjacent grains in YSZ ceramics. Herein, we propose that the intensity ratio of 2D peak to G peak of GNPs in Raman spectrum serves as a key indicator to assess the nanomechanical properties of GNPs/YSZ composites. When the intensity ratio of 2D peak to G peak is 0.5–0.6, the GNPs/YSZ composites obtained in the sintering temperature range of 1200–1250 ℃ exhibit excellent nanomechanical properties such as hardness, elastic modulus, wear and creep resistance.