Mesoporous rhombus-shaped ZnO rod arrays based gas sensors were successfully fabricated by a post-thermal conversion of rhombic Zn(OH)F precursors after a low temperature fluorine-mediated hydrothermal method. The gas sensors annealed at 350, 450, 550 and 650°C showed different responses for ethanol detection. Increasing of the annealing temperatures resulted in the decline of gas response, which is due to the effect of grain size distributions, specific surface area and defect concentration. At low temperature (less than 350°C), the incomplete decomposition of Zn(OH)F led to the instability of the sensors. The sensor annealed at 450°C showed the best performance, and the response to 100ppm ethanol reached ∼11.8 at 300°C. The sensor also exhibited good response/recovery speed (4s and 7s), excellent gas response and good stability. The fabrication of the high-performance gas sensors possesses the capability of constructing complex architectures with mesoporous rhombus-shaped ZnO rod arrays as the building block.