Abstract: With the continuous development of frequency source technology, the frequency range and phase noise level of signals are constantly improved and optimized, which poses new challenges to the accurate measurement of their phase noise indicators. In order to meet the requirement of phase noise measurement of high performance and low noise signal sources in the field of microwave radio frequency, such as radar detection, precision guidance and time-frequency reference, the principle of phase detection method is analyzed and studied, and the detection path of low noise bottom is designed. At the same time, a cross-correlation phase noise measurement system with double detection channels is designed by combining cross-correlation technology and microwave frequency conversion technology, and the noise bottom of the system is further optimized, so as to achieve the accurate measurement of the phase noise index of wide frequency range and ultra-low phase noise signal.