Civil engineering structures built on coral sand foundations in the Sea experience dynamic anisotropic stresses rather than isotropic stress. A series of undrained dynamic tests were conducted on coral sand to investigate the effect of consolidation stress ratios (Kc of 1.0, 1.5, 1.7, and 2.0) and cyclic stress ratios (CSR of 0.30, 0.35, and 0.40) on unreinforced coral sand (URCS) and geogrid-reinforced coral sand (GRCS) deformation behavior. The results showed that increasing Kc from 1 to 2 decreases axial strain and pore pressure build-up rate. The improvement is more pronounced in GRCS than in URCS. At Kc, equal 1, the liquefaction resistance of GRCS at ɛa ≥ 5% increased by about 87% compared to URCS samples. Cyclic mobility deformation was observed in both GRCS and URCS at Kc, equal to 1. In contrast, a permanent plastic deformation pattern was noticed in both GRCS and URCS samples at Kc higher 1. The stiffness of both GRCS and URCS improves with increasing Kc, and the improvement is pronounced in GRCS, especially at a CSR of 0.30. Particle breakage was found to increase with increasing CSR, input energy, and Kc, and the breakage is significantly higher in the GRCS than in the URCS.