A novel pressure sensor based on single-longitudinal-mode distributed Bragg reflector (DBR) was reported. DBR will induce birefringence under external press on the cavity. According to this, this laser can be used to sense external pressure by measuring the polarization mode beat-frequency shift. And as the beat-frequency ranges about 1 GHz, the demodulation is much easier to realize. Experiment proves that the beat-frequency ranges from 800 MHz to 1200 MHz when the pressure ranges from 0～1.2 N, and the degree of fitting is 99.76%. The sensor keeps the strong points of FBG sensing while its signal demodulation is quite convenient and exact.