The three-dimensional (3D) WO3 hollow microspheres assembled by single-crystalline nanosheets have been successfully synthesized using a simple low-temperature solvothermal strategy followed by an annealing process in atmosphere. The morphology analysis reveals that the entire growth of WO3 hollow microspheres which mainly includes sphere formed and sphere hollowed these two processes. The as-fabricated WO3 hollow microspheres based sensor exhibits high selectivity and short response time (similar to 1.5 s) towards 50 ppm triethylamine (TEA) detection at 220 degrees C, which is better than almost all of the reported TEA sensing sensors. The unique 3D hierarchical hollow and porous structure can be associated with the ultrafast gas-sensing performance. The excellent gas-sensing properties and simple synthesis route demonstrate WO3 hollow microspheres could be a promising candidate as a TEA gas-sensing material.