A transconductor circuit used in a mixer for canceling second-order inter-modulation distortion includes a first transistor and a second transistor, of which the base (gate) ends coupled to a first input end and a second input end, for receiving a differential input signal; and a negative feedback circuit, of which the input end coupled to the emitter (source) ends of the first transistor and the second transistor, of which the out end coupled to the base (gate) ends of the first transistor and the second transistor, for adjusting the voltage of the base (gate) of the first transistor and the second transistor according to the difference between a reference voltage and the detected voltage of the emitter (source) of the first transistor and the second transistor.