MoO₃gas-sensing materials with different Ni²⁺doping concentration were prepared by a simple one-step sol vothermal method. The phase structure, micro-structure and morphology of the as-prepared samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and the transmission electron microscope (TEM) etc., respectively. The morphology can be changed by adjusting the doping concentration of Ni²⁺. Among them, the 5 mol% Ni-doped MoO₃sample with a pompon-like morphology improved gas accessibility significantly. Prominently, the response of the sensors on xylene was increased 18 times from 3.48 to 62.6, the response time was about 1 s and the best selectivity was obtained at the optimum temperature of 250 °C. These breakthroughs are attributed to the increase of surface-active sites and the im provement of micro-morphology caused by Ni²⁺doping.