Abstract: To meet the increasing demand for efficient computation of electromagnetic scattering characteristics of space targets, this paper presents a high-efficiency methodology that integrates the Compressed Block Scheme (CBS) with the Multilevel Fast Multipole Algorithm (MLFMA). This approach effectively addresses the challenges associated with the substantial size of the near-field impedance matrix and the limited efficiency of iterative solutions in calculating the electromagnetic characteristics of space targets. Specifically, it employs the octree chunking operation of MLFMA to partition the near-field impedance matrix into multiple sparse matrix blocks, while utilizing CBS for compressed storage. This integration significantly reduces memory requirements and accelerates sparse matrix-vector multiplication. Furthermore, the storage requirements are further minimized by sharing the source function index during the storage process. Experimental results obtained from models of spheres, cubes, amygdalae, and satellites indicate that this method enhances computational efficiency while preserving high accuracy, thereby rendering it suitable for the rapid and precise determination of the electromagnetic scattering properties of space targets with complex structures.