Abstract: The study used seawater, sea sand (SS), and coral aggregates (CA) to replace river water, natural river sand, and natural coarse aggregates, respectively, to prepare seawater sea sand coral aggregates concrete (SSCAC). However, due to the rough and porous surface of coral aggregate, the friction between the slurry and it increases, thereby affecting the gap permeability of seawater sand coral concrete. The key to solving this problem lies in optimizing the rheological properties of seawater sand coral concrete, which can be achieved by adding silica fume (SF) instead of some cement, and using an appropriate amount of superplasticizer (SP) to increase the wet packing density (WPD) of seawater sand coral concrete. This experiment designed a total of 12 sets of seawater sea sand coral concrete mix proportions with different silicon powder substitution rates (0% and 10%) and different water reducing agent dosages, and tested their flowability, gap permeability, wet bulk density, segregation index, and compressive strength. The results showed that the addition of appropriate amounts of silicon powder and water reducing agents increased the wet packing density of seawater sand coral concrete, thereby improving its anti segregation performance, enhancing its flowability, and ultimately improving its gap permeability.