The invention discloses an L-band single-way bias low-noise cryogenic amplifier, wherein the amplifier comprises an input matching circuit, a direct current biasing circuit, a signal amplifying circuit and an output matching circuit; an output end of the input matching circuit is connected with an input end of the direct current biasing circuit and an input end of the signal amplifying circuit; an output end of the signal amplifying circuit is connected with an output end of the direct current biasing circuit and an input end of the output matching circuit. The L-band cryogenic amplifier of the application, whose working band is 1.3 to 1.8 GHz, can work steadily under ultralow temperature of 10 to 20 K for a long time, and the low-temperature environment greatly reduces resistance thermal noise of resistive elements of the low-noise amplifier and gate-drain junction noise of transistors, thereby reducing the equivalent noise temperature of the low-noise amplifier to about 9K. The selection of the transistors and the design of the direct current biasing circuit enable the low-noise cryogenic amplifier to have a wide dynamic range, and the low-noise cryogenic amplifier has an output three-order cut-off power of up to 25.5dBm and an output 1dB compression power of up to 15dBm.