An ultra wideband tunable microwave photonic filter based on high birefringence photonic crystal fiber and fiber ring was proposed. The multi-wavelength fiber laser was used as the light source, and the high birefringence photonic crystal fiber was filled with temperature-sensitive liquid. The high birefringence photonic crystal fiber could own different birefringence by varying the temperature of temperature-sensitive liquid, and the laser output with different wavelengths was obtained, making the microwave photonic filter have different free spectral range. The simulating results show that when the temperature is changing from 20℃ to 80℃, the free spectral range of filter has the range of 2.49 GHz to 39.9 GHz. By introducing the fiber ring cascade in the microwave photonic filter, the main sidelobe suppression ratio of the filter can be raised to 33.6dB and the maximum Q-value of 499 can be obtained, which improve its frequency selectivity effectively.