Substoichiometric tungsten oxide (WO3-x) has become one of the interesting candidates for localized surface plasmon resonance (LSPR) hosts because of its fascinating properties. Herein, we report that substoichiometric WO3-x can be fabricated via a facile solid phase reduction method, and at the same time it exhibits a strong LSPR in the near infrared region. Tunable plasmon resonances can be observed in a wide range by changing their stoichiometry. In the bovine serum albumin (BSA) based optical bio-sensing system, the plasmonic WO3-x displays superior sensitivity. Moreover, the hybrid nanocomposites combining the plasmonic WO3-x and plasmonic Ag can be also obtained, which show great potentials in heterogeneous catalysis. Specially, the WO3-x prepared at the reduction temperature of 350 degrees C (WO3-350) exerts improved photocatalytic performance toward methylene blue degradation, which is due to the synergistic effect of the strong plasmonic effect of WO3-350 and Ag nanoparticles.