Abstract: In order to optimize the phase noise characteristics and improve the performance of an optoelectronic oscillator (OEO), the relation among the phase noise of an OEO, the spectra line-width and optical power was studied by theoretical analysis and experimental verification. The spectral performance and phase noise of microwave signals generated by the OEO were measured respectively, under the conditions of equal optical power and different spectra line-widths. And then, phase noise of microwave signals was measured under the conditions of fixed spectral line-width and different laser power. The results indicate that the narrower spectral line-width and the higher laser power, the better phase noise and spectral characteristics of microwave signals. Furthermore, compared with the spectral line-width, the laser power has greater effect on phase noise beyond 1kHz frequency offset. The result is helpful for improving phase noise of photoelectric oscillator.