摘要： The porous ZnO nanorods were successfully synthesized by a two-step template free method consisting of a modified hydrothermal approach and subsequent annealing treatment. Additive formaldehyde was adopted in the initial hydrothermal approach. Numerous mesopores with orderly distribution along the c axis apparently appeared in the annealed products. It is suggested that formaldehyde might adsorb in ZnO nanorods during the hydrothermal process and decompose under elevated temperature. The release of the generated gas prompted the formation of the pores. A schematic model was proposed to describe the forming of pores in ZnO nanorods. Further investigation demonstrated that the emission behavior and crystallographic quality may highly depend on the annealing temperature. The intensity ratio of the ultraviolet emission peak and visible emission peak as well as the crystallographic quality fluctuates due to the competition of the forming of pores and annealed temperature. The samples annealed at 450 °C possess high crystallographic quality and large surface area, which may be the suitable candidate for highly effective photocatalyst and ZnO based photoelectric devices.