Abstract: Weak signal acquisition plays a crucial role in current field based through-the-earth communication system. In this paper, we improve the traditional sliding correlation acquisition algorithm and propose a weak signal acquisition algorithm in through-the-earth communication. Ultra-Wideband (UWB) pulse shape modulation and high gain spread spectrumis is adopted by communication system.,and each chip is modulated as a waveform that is similar to a Gaussian derivative pulse with positive and negative peaks. The received signal is sampled and quantized at a rate of 16 samples per chip and divided into 16 channels according to the time tapping technology. Each channel uses the same PN code correlator for sliding correlation despreading. Sixteen correlation values can be obtained and the difference between the two of them are used as a decision parameter. Both theoretical analysis and simulation results validate that the proposed algorithm shows a great advantage over the conventional one about 7.2dB.