Abstract: A vacuum-assisted compression molding and free curing method suitable for the preparation of epoxy resin-based solid buoyancy materials was proposed by learning from the ceramic material molding process, which realized the separation of molding and solidification during the preparation of solid buoyancy materials and provided a new method for the preparation of high performance solid buoyancy materials. The epoxy resin (E-4221) was used as the matrix, and the hollow glass microsphere (HGMS) was used as the filling material. The HGMS/E-4221 solid buoyancy material with high HGMS volume fraction was prepared by compression molding and free curing method. The effects of volume fraction of HGMS and molding pressure on the density, compressive strength and water absorption of HGMS/E-4221 solid buoyancy materials were studied. The results show that the vacuum-assisted compression molding and free curing method is suitable for the preparation of HGMS/E-4221 solid buoyancy materials with HGMS volume fraction of 65%-67%. The obtained HGMS/E-4221 solid buoyancy material has a den-sity of 0.621-0.655 g/cm³ and a suitable depth of 8 000-10 000 m.