Abstract: In order to solve the problem of the null detection point in the vital signs detection based on continuous wave(CW) Doppler radar, a novel dual-band hybrid down-conversion radar transceiver system is proposed. The proposed radar system operating frequency is 2.05 GHz and 1.64 GHz. Correlation between signals can improve the overall performance of the system. At λ/4 distance, the single-band single-channel detection has the problem of null detection point, and the proposed dual-band double-channel detection can solve the null detection point. On the other hand, at the non-λ/4 distance, the results of the dual-band detection double-channel can be mutually verified, ensuring the detection accuracy of the vital sign detection system. The simulation results prove the feasibility of the radar system. Regardless of whether the detected distance is at the λ/4 distance, the proposed vital sign detection system can always obtain the vital sign.