The dimension condition of multilayer cylinder sapphire-loaded-cavity resonator to meet the requirement of Bragg mode was analyzed. The single layer cavity was simulated and designed and the Teflon support was used to fix the sapphire in the inner-silver-plated cavity. A test showed that the Bragg mode is realized at 9.7GHz and the quality value is greater than 200,000. The Bragg mode is being used as band pass filter to build X band oscillator, which includes low noise amplify, filter and mechanical phase shifter. The oscillator realized stabilization by choosing proper insert loss and adjusting phase shifter. A secibd test showed that the oscillator has low phase noise output and is vulnerable to environment temperature. As ultra high quality value sapphire resonator is being used, the oscillator has the potential to be the state-of-art X band frequency standard with lowest phase noise at room temperature.