Abstract: Low-noise amplifier is an important component in radio astronomical front-end. It will affect the sensitivity of receiving system directly. In this paper, an ultra-wideband monolithic microwave integrated low noise amplifier based on 70nm GaAs mHEMT process from OMMIC has been designed. The 2-18GHz frequency coverage of MMIC LNA covers traditional four astronomical bands, such as S-, C-, X- and Ku-band. It is suitable for the application on the ultra-wideband receiver development for centimeter wave length, and ultra-broadband IF amplifier module for millimeter wave length astronomy. With the DC power dissipation of 150mW, the measured results show that the 3-stage MMIC LNA achieves the gain over 28dB, and the average noise temperature is about 93K.The chip size is 2mm × 1mm.