Uniform poly(2-aminothiophenol) nanofibers embedded with highly dispersed gold nanoparticles have been fabricated through a facile templateless one-step method. The diameter of composite nanofibers can be controlled in the range of 200-80 nm by simply tuning the speed of mechanical stirring during materials synthesis. Results from our work will provide insight into the shape-controlled synthesis of other nanomaterials by simply introducing mechanical agitation. Removal of gold nanoparticles in composite nanofibers leads to polymer nanotubes with continuous or incontinuous nanocavities depending on mechanical stirring speeds. Furthermore, morphology-dependent catalytic performances of such composites are also investigated.