This paper presents development of millimeter wave FMCW Doppler radar front-end module in 3D integrated technology. The radar transceiver system works at Ka-band frequency, in which the MMICs are all embedded in a high resistance silicon wafer. The RF signal is interconnected by Au-BCB-Au structures. The dimension of this integrated SiP system was 8.7mm*6.1mm. According to the measured results, the transmitted power was more than 12 dBm within the operating frequency 32GHz, and the SNR(Signal to Noise Ratio) of reflection object’s Doppler signal is 9dB, which can meet with the miniaturized requirements of the radar system.