A transconductance-enhancing passive frequency mixer comprises a transconductance amplification stage, a frequency mixing stage, and an output transresistance amplifier. The transconductance amplification stage has a pre-amplification transconductance-enhancing structure, so that the transconductance is greatly enhanced, thereby obtaining the same transconductance value at a lower bias current. A radio-frequency current is modulated by the frequency mixing stage to generate an output mid-frequency current signal. The mid-frequency current signal passes through the transresistance amplifier, to form voltage output, and finally obtain a mid-frequency voltage signal. The transresistance amplifier has a transconductance-enhancing structure, thereby further reducing input impedance, and improving current utilization efficiency and port isolation. The frequency mixer has the characteristics of low power consumption, high conversion gain, good port isolation, and the like.