Abstract: Due to the inhomogeneity of graphene composites (GC) made of randomly stacked graphene, the piezoresistive sensing performance of GC is closely related to the size of meso element. According to the microstructure characteristics of GC, a calculation method for piezoresistive sensing performance of GC was developed. The electron percolation probability, initial sheet resistance and relative resistance-strain relationship of GC were calculated in turn. The results show that the electron percolation probability of GC increases with the increase of graphene area fraction. The percolation threshold of GC with large aspect ratio graphene is lower, and the minimum area fraction of graphene to keep the electron transport network connected is 0.5. The minimum side length of GC representative element can be determined by its initial sheet resistance. GC with large area fraction has smaller representative element, and the minimum ratios of the side length of representative element with area fraction of 1.2, 1.4, 1.6, 1.8 and 2.0 to graphene side length are 35, 30, 25, 20 and 15, respectively. Finally, the calculation results of GC representative elements confirm that the linear sensing stage and total sensing range of GC can be enlarged by increasing the area fraction or aspect ratio of graphene.