To meet the application requirements for small size, low insertion loss, and high stopband suppression in intermediate frequency ultra-narrowband filters, AT-cut thickness vibration fundamental mode piezoelectric quartz crystal resonators, configured with a differential bridge-type circuit, have been utilized. This design achieves a working frequency of 10.7 MHz, a 3 dB bandwidth of 0.8 kHz, in-band fluctuations of less than 0.5 dB, an inser tion loss of less than 4 dB, and stopband suppression greater than 70 dB. The resulting crystal filter fulfills the pro ject requirements and offers a design framework for the development of future ultra-narrowband crystal filters.