Time reversal (TR) is an effective method to solve the multipath effect and energy dispersion of ultra-wideband signals by retransmitting the received signals to the scattering environment to achieve spatial-time focusing. The TR transmitted signal needs to be extracted from the received echo. However, in the case of a low signal-to-noise ratio (SNR), it is difficult to determine the position of the target signal in the received data of pulse radar. In this article, we propose a method to extract the start and end positions of the target signals in the echo. For low SNR echoes, the mean average filter and autocorrelation accumulation are used to remove noise. Then, the binary integration energy detection is applied to determine the position of the target signal in the echo. The simulation results illustrate that the proposed method can accurately extract the target position, which can be further used as the TR transmitted signal.