A Doppler radar array is developed for two-dimensional noncontact vital sign detection. The radar array includes four detectors, an 8-channel data acquisition module, and a computer for spectrum analysis. Each of the detectors consists of a radio frequency transceiver, a baseband analog circuit, and a power management circuit. Using the radar array, cancellation of the noise from planar random walk of human body is achieved. The radar array also strengthens the detecting sensitivity on the respiration and heartbeat and its principle is discussed. A DC offset compensation algorithm is introduced to free the body movement cancellation from disturbance of unwanted DC offset. Experiments were performed with a human subject in lab environment. Results were analyzed to verify the improved detection performance at the presence of two-dimensional human body movement.