The paper presents the design and temperature control of a low phase noise sapphire oscillator. Utilizing the theory of sapphire resonator, finite element simulation software is employed to accomplish the design process. The measured center frequency of the sapphire resonator is 9.84 GHz with a loaded Q value of 113000. By utilizing the sapphire resonator as a frequency selection network along with components such as amplifier, filter, phase shifter and coupler, a low-noise sapphire oscillator is constructed. The output frequency of this oscillator is 9.84 GHz with an output power of 9 dBm. It exhibits excellent performance in terms of phase noise: -117 dBc/Hz at 1 kHz deviation from the carrier, -144 dBc/Hz at 10 kHz deviation from the carrier, and -161 dBc/Hz at 100 kHz deviation from the carrier. This oscillator significantly enhances radar capabilities for the detection of low-speed and small targets.