Abstract: Traditional millimeter-wave switching integrated circuits regard transistors as on-off units in series or parallel architecture, but the quarter wavelength lines used in the matching process will increase the loss and area of the switching circuit, increase the processing cost, and reduce the loss of the RF front-end transmission channel. This paper proposes a single-knife single-throw switch design method based on the basic unit of switching circuit. By analyzing the equivalent parasitic parameters of the transistor, the conduction state is high pass filter to reduce the circuit loss at high frequency and the off state is series parallel resonance to realize the signal isolation in the off state. Using this method to design and realize a single knife throw switch applied to the millimeter wave frequency band on the 0.1 μm GaN process, and the overall chip area is 0.75 mm×0.75 mm. The test results show that in the working band of 24 GHz ~30 GHz, the on state loss is less than 1.2 dB, the off state isolation is greater than 16 dB, and the input and output echo loss is greater than-12 dB.