Abstract: A design method of differential reflection-type passive phase shifter was studied for K-band phased array transceiver system. A 5-bit phase shifter was fabricated in TSMC 90 nm CMOS technology. The reflective load was made up of an inductor and a varactor in parallel connection. Measurement results show that, the phase error is less than 6° from 23 to 25 GHz and less than 15° from 22 to 26 GHz. Based on the same process, an improved 6-bit phase shifter was proposed. A MOM (metal oxide metal) capacitor array with a relatively high quality factor was used to replace the traditional varactor of the reflective load. The capacitance value change was carried out by switch control. Simulation results show that the phase error of the new phase shifter is less than 4° from 23 to 25 GHz and less than 8° from 22 to 26 GHz.