In this paper, detection technology using Ultra Wideband electromagnetic wave is introduced into disaster rescue, so as to give full play to its strong penetrating ability, large detection range, high resolution and rich information of target. In order to study the feasibility of detection of human body behind the obstacle using Ultra Wideband electromagnetic waves, taking the life model behind the obstacle as an example, the three Dimension propagation process of ultra-wideband electromagnetic wave is simulated using finite difference time domain (FDTD) method. The simulations of human body return reflected by different state of chest within a respiratory cycle, and the strengthened integration curves of fretting signal in many different state of chest are given. The results show that Ultra Wideband electromagnetic wave can reflect the human body behind the wall and obstacle with high resolution can detect respiratory signal caused by chest movement. Thus it's feasible that ultra-wideband electromagnetic detection technology is used in disaster rescue, and it has a unique advantage in penetrating ability. Research results provide electromagnetic detection method and mathematical simulation technology for the urban disasters and emergency assistance, and lay a foundation for the establishment of a new, non-contact, and effective disaster rescue practical technology.