Abstract: FMCW radar has the advantages of good anti-interception performance and small range blind area, so it plays an important role in modern radar system. However, the self-interference signal caused by the transmission leakage seriously affects the sensitivity of the receiving system. This paper first analyzes the principle of self-interference, gives a simplified model of self-interference based on FMCW system, analyzes the relationship between receiving link dynamics and system noise figure, deduces the functional relationship between system noise figure deterioration value, ENOB value of digital-to-analog converter and leakage power, defines ADC noise deterioration index, and then analyzes the influence of FMCW de-slope receiver phase noise on radar sensitivity. The inherent relationship between radar operating range, transceiver isolation and phase noise in FMCW system is revealed. Finally, it is concluded that transceiver antenna isolation and phase noise index are the key indicators to improve the power of FMCW radar. Related theories and mathematical models provide an important reference for subsequent product research and development.