Nanostructured WO3 mixed with chloroplatinic acid was prepared by solgel method. Fiber Bragg grating was coated with the hybrid material. The asprepared powder was mixed with different ratio of chloroplatinic acid and annealed at different temperatures and their structures were characterized by Xray diffraction. The results show that the crystallinity of WO3 increases with the decrease of chloroplatinic acid and the increase of thermal treating temperature. The experiment demonstrates that after being annealed under 30℃ with the Pt∶W ratio of 1∶9, the sensor has good repeatability, can reach the response speed of 15 s to 4% Hz, and has 140 pm central wavelength change. The sensor shows no sensibility with further increase of temperature up to 500℃.