Different from ground communications， space communications usually involve signal vehicles that travel over long-distance at a high speed. In these scenarios， the signal transmission faces two difficulties： A low signal-to-noise-ratio （SNR） caused by the long-distance path-loss and a dynamic Doppler-shift caused by the high-speed movement. For Doppler-shift acquisition， the low SNR requires a long-time accumulation to accumulate a large number of signals. However， during this period， the dynamic Doppler-shift disperses all signals’ total energy over a wide frequency range. To address the energy dispersion problem， this paper proposes a local-clustering-acquisition （LCA） algorithm. The LCA algorithm uses the largest elements from the global-ranges to construct a local-range， then selects some large elements from this local-range for clustering， and finally searches the largest cluster from the clustering results to obtain the acquisition result. Theoretical analysis and simulation validation results demonstrate the LCA algorithm’s significant advantages in increasing acquisition probability， as compared with the existing algorithms.