Aiming at the problem that wireless receivers need to amplify the signals of different intensities to different degrees, a variable-gain low noise amplifier operating in the 5G communication band from 3 to 5 GHz was designed in WIN’s 0.15 μm GaAs pHEMT process. The amplifier included two stages of amplification circuits, both of which adopted a self-biased structure to reduce the number of ports, and the continuously adjustable range of the system gain of about 39.3 dB (-3.5-35.8 dB) can be achieved by adjusting the control voltage of the second stage amplification circuit to vary from 0 to 5 V. The footprint is 0.94×1.24 mm2. At a control voltage of 0 V, the system noise is 0.53±0.01 dB, and the gain is 35.5±0.35 dB. At the center frequency point of 4 GHz, the OP1dB is 13.2 dBm, and the OIP3 reaches 32.7 dBm, indicating that the system has a good linearity.