We have successfully prepared a floating-typed surface-enhanced Raman scattering (SERS) substrate by the uniform nanoparticle arrays of silver nanoparticles (AgNPs) immobilized on the dendron-exfoliated reduced graphene oxide (rGO) nanosheets. These poly(urea/malonamide) dendrons were precisely synthesized, and then grafted on the dendron-exfoliated rGO nanosheets based on an efficient building block of dual functional 4-isocyanato-4'-(3,3-dimethyl-2,4-dioxo-azetidino)-diphenylmethane (IDD). By using dendron-rGO nanosheets as templates for hosting AgNPs, the particle size (D) and interparticle gap (W) of AgNPs could be manipulated by the incorporation of dendrons of various generations (0.5, 1.5, and 2.5 generations), evaluated by transmission electron microscopy. The results indicate that the nanohybrids with 1.5 generation-dendron exhibited stable, enormous, and linear-quantitative Raman enhancement in malachite green detection (1-100 ppm), due to the lowest W/D ratio (0.85 +/- 0.60) and interparticle gap (7.60 +/- 5.29 nm). The limit of detection (LOD) of malachite green is lower than 2.7 x 10(-11) M (0.01 ppb). AgNPs@rGO-dendritic derivative nanohybrids as floating and flexible SEAS substrates provide ultrasensitive and stable SEAS detection in the solutions, which offers great potential for practical applications in detecting environmental pollutants.