The phase noise within the half-bandwidth of the loop is closely related to the loaded quality factor QL. The importance of loaded quality factor QL and the method of reducing phase noise on the basis of improving QL are analyzed in this paper. Formulation of QL is derived from analysis of the Pierce oscillator circuit, and calculated with commercial numerical analysis software. According to the results, we can draw a conclusion that QL is explicitly related to circuit pa rameters. Based on this conclusion, a design of the prototype 120-MHz crystal oscillator is presented and the experiments are carried out. The crystal resonator utilized is an SC-cut 5th-overtone crystal resonator with an unloaded quality fac tor Q0 of about 1.05 × 105. The circuit parameter values are adjusted to make QL reasonably higher, while maintaining an output amplitude of 2 to 3 dBm. The measurement results of near carrier frequency phase noise are -104 dBc/Hz at 10 Hz and -134 dBc/Hz at 100 Hz. Experimental results show that it is feasible to design a low-phase-noise crystal oscillator based on improving QL.