WO3-Pd composite films were deposited on the side-face of side-polished fiber Bragg grating as sensing elements by magnetron sputtering process. XRD result indicates that the WO3-Pd composite films are mainly amorphous. Compared to standard FBG coated with same hydrogen sensitive film, side-polished FBG significantly increase the sensor's sensitivity. When hydrogen concentrations are 4% and 8% in volume percentage, maximum wavelength shifts of side-polished FBG are 25 and 55 pm respectively. The experimental results show the sensor's hydrogen response is reversible, and side-polished FBG hydrogen sensor has great potential in hydrogen's measurement.