We present the preparation of plasmonic WO_3-x nanowires via a surfactant-free solvothermal process which generates massive oxygen vacancies on WO_3-x nanowires. As a result, the obtained WO_3-x nanowires exhibit intensive LSPR absorption in the visible and NIR region. The surface plasmon excitation of WO_3-x nanowires under visible/NIR light irradiation leads to significantly enhanced activity for hydrogen evolution from ammonia borane as compared to that in dark condition. The enhancement is attributed to the hot plasmon electrons that promote charge transfer between the reagents for hydrogen evolution on the WO_3-x nanowire surface. In addition, the photothermal effect would supply additional localized heating on the WO_3-x nanowire surface, and thereby increase reaction rate for more efficient H₂ evolution. Furthermore, we also demonstrate that the plasmon excitation of Pd-loaded WO_3-x nanowires by long wavelength irradiation can greatly promote chemical reactions catalyzed by the attached Pd nanoparticles.