A simple novel fiber Bragg grating interrogating system is proposed and experimentally demonstrated based on interference of polarized mode. The essential part of the system is only comprised of a high birefringence fiber with fiber reflector and a fiber polarizer. The vibration micro-nano signals from 0.1 Hz to 7.9 kHz were picked up with fidelity. Measurements of dynamic strains with resolutions of 0.5nε/Hz were demonstrated. The results show that the system is suitable for wide frequency range, micro-nano range of dynamic strain detection. This system potentially offers a low-cost and high-performance solution for the interrogation of FBG sensor.