The zinc oxide whiskers were synthesized by the equilibrium gas expanding method at the temperature of 700 C with metallic zinc as the main raw material without any catalysts. The effects of the growth time on microstructure and photoluminescence properties were investigated. The results show that the as-grown samples are composed of uniform tetrapod-like ZnO whiskers. The length and diameter of the arms of the tetrapod-like ZnO whiskers increase obviously with the increase of the growth time. The strong single ultraviolet （UV） emission centering 385-391 nm without any accompanying deep-level emission is observed in the room temperature photoluminescence （PL） spectra of the whiskers. The intensity of UV emission increases markedly with the increase of growth time.
