This paper is based on the general principle of beamforming algorithm of array signal processing. It gives a kind of high precision adaptive time-domain beamforming algorithm, uses ultra-wide band (UWB) microwave signal as an emission source applied to the human body in early breast cancer detection. In this paper, we build a two-dimensional, semicircle breast tissue model, use numerical simulation with finite-difference time-domain (FDTD) method for detection. The result shows the superiority of beamforming algorithm compared with that of confocal imaging algorithms and beamforming algorithms, especially to the Capon beamforming algorithm.