The ultra-wideband receivers face many technical challenges, and one of the key technical difficulties is the ultra-wideband low-noise amplifier (LNA). Using a gallium arsenide material-based 70nm gate length metamorphic high electron mobility transistor, and dual-supply bias 4-stage amplifier circuit structure, a 4-40GHz ultra-wideband low-noise monolithic microwave integrated amplifier is designed, which completely covers 5 bands of C, X, Ku, K and Ka. The design simulation results show that the amplifier gain is (40 ± 2.5)dB. The average noise temperature at room temperature is 95K, the noise temperature of 4-12.5GHz is lower than 83K in the whole frequency band, and the DC (direct current) power consumption is 130.5mW. The input reflection coefficient in the entire frequency band is typically -10dB, and the output reflection coefficient is typically -15dB, stable in the whole frequency range, no self-excited oscillation phenomenon. The device can be used in the ultra-wideband receivers and large-scale multi-beam receivers, which improve the observation efficiency of radio telescopes effectively.