Abstract: In this paper, the transmitted signal model, the target signature model and the received signal model of UWB radar used for urban emergency search and rescue, are presented. More than that, the relationship between the range resolution of radar and the duration of the transmitted UWB-pulse, the time separation between the pulses, the length of the transmitted signal, have also been analyzed. The signal models are all simulated on the Matlab and good conclusions are drawn from them. When the width of signal pulse of radar is smaller, the UWB property of the signal disappears gradually. Multi - scatter - centers reduces to one, the range resolution of radar becomes worse, the image of radar turns more illegible.