Abstract: The Bragg wavelength demodulation technology based on phaseshift fiber grating is proposed. One or more spectral windows with very narrow linewidth can be opened by the phaseshift fiber grating in the reflectance spectrum stopband, and the windows are moved with the variations of the phase shift linearly. In order to implement Bragg wavelength demodulation, the electric current tuning phaseshift technology was utilized in the experiment. The measurement temperature could reach 200℃ and the strain could reach 2000με when the phaseshift fiber grating with maximal wavelength offset of 2nm was used to do the tunable filtering. The experiment shows that the Bragg wavelength demodulation by the phaseshift fiber grating has reached the expected result. A new method is established to solve the demodulation of Bragg wavelength.