Abstract: In order to know the development and to predict the possible trends of through-the-wall detection, this article reviews the development of human target detection behind the wall in the field of through-wall radar research in recent years. Aiming at the three key technologies involved in human targets detection behind the wall, micro-Doppler spectrum recognition, two-dimensional moving target detection, and high-resolution three-dimensional imaging of human targets, we summarized the relevant literature published at home and abroad. The results show that through-the-wall radar has made great progress in application fields such as life feature extraction, motion behavior monitoring, and gesture recognition. With the development of related research, through-the-wall radar systems are beginning to show characteristics of lightweight, miniaturization, and low cost, and the corresponding processing algorithms are moving more intelligently.