There dimensional (3D) metallic nanohybrids have attracted attentions for the applications in nanophotonic devices, catalysis and biosensor. Here, the 3D suspended Ag nanoparticles/Carbon nanotubes (AgNPs/CNTs) nanohybrids, obtained by self-aggregating AgNPs onto the suspended CNT networks, are synthesized and used for the SERS application. The electric field distribution with the near-field and far-field coupling can be obtained by the optimization of the nanogaps of the AgNPs. Such suspended AgNPs/CNTs nanohybrids are studied to be used as the ultra-sensitive SERS biosensor, benefiting from the bio-compatibility and chemical absorption of the CNT networks and the EM enhancement of the 3D denser "hotspots". R6G molecules with a concentration as low as 10(-15) M can be clearly detected, demonstrating their excellent Raman enhancement.