A 3-10 GHz broadband CMOS T/R Switch for ultra-wideband (UWB) transceiver is presented. The broadband CMOS T/R Switch is fabricated based on the 0.18 um 1P6M standard CMOS process. On-chip measurement of the CMOS T/R Switch is performed. The insertion loss of the proposed CMOS T/R Switch Is about 3.1±1.3dB. The return losses at both input and output terminals are higher than 14 dB. It is also characterized with 25-34dB isolation and 18-20 dBm input P1dB. The broadband CMOS T/R Switch shows highly linear phase and group delay of 20±10 ps from 10MHz to 15GHz. It can be easily integrated with other CMOS RFICs to form on-chip transceivers for various UWB applications.