Abstract: By analyzing the low temperature characteristics of HEMT devices and the application of cryogenic LNA,this paper presents the design of broadband LNA used for VHF/UHF band, from the perspectives of device selection and circuit stability influenced by circuit topology. This paper expounds the importance of stability considered in design process for circuit matching. From the concrete example, the design method of improving the stability of the circuit and the matching of standing wave and noise are given. The analysis of the test results ( relative bandwidth390%; noise figure￡0.3dB@77K;return loss￡-18dB) and application effects of cryogenic LNA proposes that the design technology involved in this paper can　guide the design and development effectively, which is of great reference significance.