Gold nanoparticle decorated lysozyme microtubes, with the diameters of 1-2 mu m and lengths on the order of millimeters, were spontaneously formed via a simple aging process of the lysozyme-gold nanoparticle aqueous solution under ambient conditions for 1 week. These novel microtubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX), as well as Fourier-transform infrared (FTIR) spectroscopy. It was confirmed that the microtubes were made up of the protein lysozyme. In addition, formation,of the microtubes was accompanied by a decrease in lysozyme concentration in the sample solution, which also indicated that these microtubes originated from lysozyme. The formation of microtubes was attributed to the formation of hydrogen bonding networks between the lysozyme molecules. Partially unfolded lysozyme molecules on gold nanoparticles probably seed the formation of the lysozyme microtubes. These novel protein microtubes not only provide some useful insights for protein study but may also have the potential to be used in the biomedical field.