SnS₂/ZnS microflower structures are prepared by one-step hydrothermal method. The microflower structures with different components are obtained after calcinating SnS₂/ZnS in air atmosphere. The influences of calcination temperature on the components and gas-sensing properties of microflower structures are investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), transmission electron microscopey (TEM), and gas sensitive characteristic analyzer. The results show that the gas-sensing performance to NO₂ at room temperature of SnO₂/ZnS microflower structure (SZ-450) is better than that of microflower structure calcinated at the other temperature. The response of SZ-450-based sensor to 10^–4 NO₂ at room temperature can reach 27.55, the response/recovery time is 53 s/79 s, the theoretical detection limit is as low as 2.1×10^–7, and it has good selectivity, repeatability, and stability. The analysis indicates that the excellent room-temperature gas-sensing characteristic of SZ-450 is related to the heterojunction between SnO₂ and ZnS. This work can provide sensitive materials for room-temperature NO₂ gas sensor and promote its development and application.