Endowing compressibility and conductivity into graphene sponge offers the possibility to regenerate piezoresistivity and is therefore of great interest in the field of sensor. In this work, the highly compressible three-dimensional graphene-only sponge (CGS) was prepared through a facile method by using ammonium sulfide and ammonia solutions under mild condition. The morphologies and microstructures of the as-prepared CGSs can be controlled by adjusting the mass ratio of graphene oxide (GO) to ammonium sulfide which changed from metallic sheen bulk with leaf-shaped structure to a black sponge with cellular structure. Besides, by simply change the concentrations of GO, CGSs with different porosity, conductivity as well as mechanical strength were obtained. Moreover, the resultant CGSs show ultralow density (as low as 4.9 mg cm-3), high porosity (as much as 99.8%), great compressibility (as much as the strain of 80%), excellent stability (100 cycles) during the compression. Furthermore, the sensitive variation of electrical resistances and cycle stability were validated under the compressive strain of 50% which make them great candidates for pressure-responsive sensors, elastic conductors and other applications.