By applying Bourdon tube and tunable filter technology, a fiber Bragg grating pressure sensor is designed. The 50 GHz dense wavelength division multiplexing- based and wavelength demodulation algorithm are adopted to locate the exact position of narrowband reflection spectrum in the channel. The results of wavelength demodulation system show that the fiducial error is only 0.5% under the range of 0~6 MPa, and the resolution of the wavelength which comes from the measured experimental can reach 0.1 pm. The demodulation sensitivity of the sensor resolution is 3×10³ nW/MPa.