3D hierarchical flower-like WO3 center dot 0.33H(2)O nanostructures were synthesized via a facile solvothermal method without using any template or surfactant. After annealed at high temperature, the as-prepared WO3 center dot 0.33H(2)O would partly or fully transform into monoclinic WO3 with the morphology almost unchanged. Gas sensing properties of the sensor based on these flower-like nanostructures with the relationship of annealing temperature were also investigated systematically. The experiment results indicate the sensor shows highest response to NO2 when the annealing temperature is 500 degrees C. At the same time, the detection limit can be as low as similar to 5 ppb level. Thus, the novel flower-like nanostructures might be a promising material for designing NO2 gas sensor with high performance. (C) 2016 Elsevier Inc. All rights reserved.