Au nanoparticle-coated In<sub>0.2</sub>Ga<sub>0.8</sub>As/GaAs bilayers have been released from GaAs (100) substrate through selective wet etching of AlAs sacrificial layer, which provides a solution to implant metal nanoparticles (NPs) in the inner wall of self-rolled-up III-V semiconductor microtubes. Scanning electron microscope (SEM) reveals that the diameter of Au nanoparticle-decorated In<sub>0.2</sub>Ga<sub>0.8</sub>As/GaAs microtube is only 2.4μm, 300nm smaller than that of traditional counterparts. This phenomenon can be explained by that the surface tension of NPs and the intrinsic strain relaxation of In<sub>0.2</sub>Ga<sub>0.8</sub>As/GaAs bilayers both affect the rolling process. In order to understand the diameter reduction in Au-assistant microtubes, room temperature (RT) Raman measurements have been employed to study the strain effects reflected by the GaAs longitudinal optical (LO) phonon mode shifts when compared LO mode of microtubes with as-grown planar. The spectrum showed that there were about 10 wavenumbers and 2.6 wavenumbers red-shifts of GaAs LO for Au-assistant and non-Au-assistant structures, respectively, from which we calculated that about 2.56% and 0.66% strain change occurred. Au nanoparticle enhanced Raman shift clearly. According to this study, an approach to reduce the diameter of rolled-up microtubes was demonstrated, and this method may provide viable solution to fabricate nanotubes in the application for Lab-on-a-chip system.