Coral　gravelly　sand　is　a　special　foundation　fill　material　in　island-reef　engineering.　This　study　conducted　a　series　of　dynamic　centrifuge　model　tests　at　a　centrifugal　acceleration　of　50g　to　assess　the　dynamic　properties　of　saturated　coral　gravelly　sand.　The　centrifuge　data　was　used　to　identify　the　cyclic　shear　stress-strain　behavior,　dilatancy　characteristics,　shear　modulus　degradation,　and　damping　ratio,　and　these　dynamic　characteristics　were　compared　with　those　of　other　sands.　Numerous　negative　dilation　spikes　were　observed　at　the　shallow　layer　in　coral　gravelly　sands　when　the　excess　pore　pressure　ratios　were　at　a　low　level.　The　concept　of　transient　stiffness　was　introduced　to　evaluate　the　mechanical　evolution　during　these　occurrences.　Compared　to　saturated　terrigenous　sands,　the　shear　strain　amplitudes　in　coral　gravelly　sands　increased　with　the　reduction　of　depth　due　to　welldrained　action,　and　the　shear　stiffness　was　fully　restored　at　the　end　of　seismic　motions.　Additionally,　it　was　found　that　the　normalized　shear　modulus　of　coral　gravelly　sands　was　lower　than　that　of　coral　sands,　while　the　damping　ratio　was　higher.　The　empirical　curve　provided　by　Darendeli　could　reasonably　depict　the　shear　modulus　degradation　behavior　of　saturated　coral　gravelly　sands.