The influence of tuning circuit parameters(such as base feedback inductance Lb,negative power source resistance R1,etc.)and resonator parameters(coupling ring size,saturation magnetic susceptibility,etc.)on the phase noise of YIG-tuned oscillator was analyzed by single variable method.The experimental results show that the phase noise gets worse with increasing the feedback inductance.With the increase of negative voltage resistance,the improvement of phase noise at high-frequency is greater than it at low-frequency.It was found that the phase noise gets worse with increasing ferromagnetic resonance line width ΔH with the working frequency at low frequency.In conclusion,reducing the phase noise of a YIG-tuned oscillator is the result of comprehensively optimizing the oscillator circuit parameters according to the requirements of various indicators.