Here, AuxRh1-x alloy nanocrystals (NCs) were used to decorate W18O49 for enhanced detection of n-butanol vapor. Monodisperse AuxRh1-x alloy NCs with a tunable composition and urchinlike W18O49 were synthesized by a simple solvothermal method. AuxRh1-x alloy NCs were loaded onto the W18O49 surface by the impregnation method. A series of material characterization methods were employed to characterize the structure and morphology of as-synthesized materials. The performance of AuxRh1-x-W18O49-based sensors to n-butanol was investigated. The results demonstrated that the Au39Rh61-W18O49-based sensor had the highest response, short response time, good selectivity, excellent repeatability, and stability to n-butanol. The gas sensing mechanism was supposed, the excellent catalytic capability of the AuxRh1-x alloy NCs were believed to be a major factor in enhancing the detection of n-butanol.