A down-conversion mixer includes a trans conductance circuit and a mixing circuit. The transconductance circuit includes: first and second transconductance units cooperatively converting a differential input voltage signal pair into a differential input current signal pair; and an inductor coupled between the first and second transconductance units. The mixing circuit is coupled to a common node of the first trans conductance unit and the inductor and to a common node of the second transconductance unit and the inductor for receiving the differential input current signal pair therefrom, and mixes the differential input current signal pair with a differential oscillatory voltage signal pair to generate a differential mixed voltage signal pair.