Disclosed is a transmission gate circuit including a control voltage generating circuit, a high voltage transmission circuit and a low voltage transmission circuit. The high and low voltage transmission circuits are coupled between an input terminal and an output terminal. The control voltage generating circuit generates two voltage groups according to an input voltage of the input terminal and an enable voltage and thereby controls the high and low voltage transmission circuits with the two voltage groups respectively. When the enable voltage is high, one voltage group includes identical voltages while a difference between any of the identical voltages and any voltage of the other voltage group is not higher than a predetermined voltage; when the enable voltage is low, each voltage group includes decremental voltages. The high/low voltage transmission circuit is turned on when the enable voltage is high and the input voltage is high/low.