A class of conducting reduced graphene oxide hydrogels is prepared with various porosities, surface areas, and electrical conductivities using ethylenediamine (EDA)/functionalized graphene oxide (GO) and ascorbic acid (VC)/GO by hydrothermal method. The microstructure of hydrogels is tailored by changing the composition of materials. It is observed that the conducing network is formed by cross-linked graphene platelets, and the piezoresistive behavior of hydrogels under cyclic compressive strain shows a linear trend up to 6.8% strain when the hydrogel is prepared by adding 5 wt % of EDA in aqueous GO solution. In addition, platinum nanoparticle-decorated (Pt NP-decorated) EDA-GO hydrogel was also prepared, showing greatly improved linear strain range as high as 52.8% with an increase in compressive modulus by 873% because of the multiscale reinforcing mechanism, which is attributed to the strong interaction between Pt NPs and graphene platelets. The piezoresistivity of the hydrogels can be of great interest in the field of high-performance strain sensors.