Hierarchical hollow tungsten trioxide is fabricated by a facile method. Annealing, proton irradiation and atomic oxygen exposure are employed as the three different post-treatment processes. Effect of different post-treatment processes on microstructures and gas sensing behaviors of the as-prepared WO₃ are investigated by various characterization analyses. We have demonstrated that the response amplitude can be greatly improved by annealing and AO treatment while it became worse after proton irradiation process. The results indicate that the post-treated WO₃ can be used as a promising material for detecting acetone.