By the frequency domain analysis of phase noise, the optimization model of Lesson noise was established and the parameters in the circuit were improved. Meanwhile, the small signal model was established to optimize the parameters in the pre-suppression circuit. In this way, the phase noise and stability were studied for the cross-coupled integrated quartz crystal oscillator with RC filter. Furthermore, the circuit and layout were designed, simulated and optimized by Cadence with NUVOTON 0.35 μm process. Subsequently, the fabrication and test were carried out under the supply voltage of 3.3 V. The results indicated that the frequency of output was 20 MHz and the phase noise of the oscillator can reach -135 dBc/Hz @ 1 Hz, -156.4 dBc / Hz @ 10 kHz, and -169.2 dBc/Hz @ 1 Hz, respectively. The ripple wave was less than 81 ppm and 71 ppm, respectively, with the variation of the supply voltage in the range of ± 10% and the temperature range from -25 ℃ to 85 ℃ .