The invention discloses a passive variable frequency mixer, which is characterized by comprising an input transconductance module, a switch mixing module and a transresistance amplifier output module,which are connected in turn, wherein the input transconductance module is connected with a radio frequency signal source, and the input transconductance module is used for converting a radio frequency signal into radio frequency current; and the switch mixing module is used for converting the radio frequency current into intermediate frequency current through down-conversion. The transresistanceamplifier output module is used for obtaining an intermediate frequency output voltage on a load resistor by use of the intermediate frequency current. The passive variable frequency mixer disclosed by the invention has the characteristics of low power consumption, high conversion gain and good port isolation.