The embodiments of the present disclosure provide a low noise amplifier including: an input stage circuit; a bias circuit, adapted for providing bias to the input stage circuit; an output stage circuit; a first amplifier and a second amplifier; a first middle stage circuit, adapted for implementing inter-stage matching, signal coupling and isolation between the input stage circuit and the first amplifier; and a second middle stage circuit, adapted for implementing inter-stage matching between the first amplifier and the second amplifier, wherein the first middle stage circuit is coupled with the second middle stage circuit via the first amplifier, and the second middle stage circuit is coupled with the output stage circuit via the second amplifier. Accordingly, amplifier gain of LNA is improved without increasing power consumption.