This letter presents the design and implementation of a K-band four-element dual-beam phased-array receiver with more than 28.14 dB transmit-receive isolation in 65-nm CMOS SOI for SATCOM applications. By properly designing the inter-stage and output matching networks of the four-stage low noise amplifier, the isolation between the transmit and receive chains of the full-duplex shared-aperture phased-array antenna system can be effectively enhanced to meet the practical requirements. In addition, to meet the demands of precise phase shifts of phased-array systems, an active vector-modulated phase shifter with low power consumption, small area occupation, and positive gain is designed. Based on the proposed methodology, a K-band four-element dual beam phased-array receiver operating from 17.7 to 21.2 GHz is designed and measured. The measurement results show the transmit-receive isolation is greater than 28.14 dB, the single-channel gain is 21.48-25.31 dB, and the noise figure is 2.42-2.77 dB over the entire working frequency. Meanwhile, the measured RMS gain error and RMS phase error are less than 0.43 dB and 3.8°, respectively.