ZnO mesoscale superstructures (ZMS) with the sizes of 2 to 6 µm were synthesized by a simple solution method without any additives. The novel ZMS were assembled by numerous nanoparticles with the diameter of less than 100 nm, and no pores were found. X-ray diffraction shows that the ZMS mainly evolved in solution. The formation process of the ZMS accords to the classical theory of nucleation and growth. Photoluminescence (PL) analysis shows a sharp UV emission peak at 392 nm and a weak broad green-yellow emission peak at about 600 nm.