The microwave landing radar is a linear frequency modulation continuous wave （LFMCW） radar， which is a key instrument for “Tianwen-1” spacecraft during its entry，descent and landing （EDL） phase. Signal leakage has become the key factor that restricts the performance of LFMCW radar. In order to satisfy the requirement of small， light and high isolation radar system， this paper combines certain methods including a high isolation antenna design， intermediate frequency filtering and leakage suppression in digital signal processing. It is proved by a helicopter test that these methods can filter out the leakage and reduce the phase noise of leakage signal about 10—15 dB by analyzing data.