The invention provides a preparation method of a gallium arsenide Te-doped barrier impurity band terahertz detector with a microporous negative electrode structure. The preparation method comprises steps of making micropores, electrodes, etc. The invention also provides a gallium arsenide Te-doped barrier impurity band terahertz detector with a microporous negative electrode structure made by the preparation method of the gallium arsenide Te-doped barrier impurity band terahertz detector with the microporous negative electrode structure. The preparation method has the following advantages: through etching the microporous structure, etching areas and then defects from etching damages are reduced. Thus, dark current of the detector is reduced and detectivity is improved. In addition, by arranging the negative electrode on a high conductivity gallium arsenide substrate in the micropore, transporting paths of photo-generated carriers are shortened; possibility of capturing the photo-generated carriers by impurities and defects in the high conductivity gallium arsenide substrate is reduced; collection efficiency of the photo-generated carriers is improved; and detectivity of the detector is further increased.