Abstract: A PIN diode is used to design a high-power single-pole double-throw (SPDT) switch that works in the L-band, which can withstand a 100 W continuous wave power signal. The switch adopts a series-parallel structure, which increases the isolation of the switch while broadening the bandwidth. The microstrip line is made through thick film process and screen printing, and the micro-assembly process completes the welding and interconnection of each device, and completes the production of the switch. The switch is controlled by a bias voltage of -5 V/+30 V. The actual measurement shows that the insertion loss of the single-pole double-throw switch is less than 0. 7 dB within 1-2 GHz, the input standing wave ratio and output standing wave ratio are both less than 1.4, and the isolation is greater than 25 dB. Under continuous wave power of 100 W, the maximum diode temperature is 122.6 ℃, meet the design requirements.