Tungsten oxide (WO3) film material is applied extensively because of its electrochromic property, gasochromic property, photochromic property, electrochemistry, etc. Based on the preliminary study on the preparation and hydrogen sensing properties of platinum-doped WO3 films, we studied the optical properties of hydrogen sensitive WO3 films for surface plasmon resonance (SPR) optic-fiber micro-sensor. In this work, firstly, the structure of SPR optic-fiber hydrogen micro-sensor was discussed. Secondly, we studied the transmissivity of the platinum-doped WO3 films. Thirdly, the reflection index of the films in different environments was discussed. This work can provide theory support for the design of SPR optic-fiber micro-sensor.