Nano-sized hollow spheres self-assembled by ZnO nanocrystals have been prepared by microemulsion method with dodecyl benzene sulfonic acid sodium salt (DBS) as the modifying and protecting agent. The product was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high High-resolution electron microscopy (HRTEM) energy dispersive spectroscopy (EDS) and photoluminescence (PL) spectra. The results showed that the hollow sphere was composed of ZnO nanocrystals. And the PL spectrum showed a different emission at 438 nm. After heated the product, PL emission peak changed. A possible formation mechanism was also proposed.