In present work, porous sphere-like and coralline-like ZnO nanoparticles (NPs) are synthesized by precipitation method at different calcination temperatures (400 and 450°C). The temperature of calcinations plays an important role in formation of NPs morphology. A formation mechanism of porous sphere-like ZnO NPs is proposed. The response of gas sensing for different concentrations of acetone (1–10,000ppm) at optimum temperature (310°C) is shown. Besides, the ZnO NPs (400°C) exhibits fast response and recovery time (average value is about 9s and 6s). These results demonstrate that the ZnO NPs (400°C) can be used as an ideal candidate for fabricating high response (130–100ppm) acetone sensor.