[Purposes] The paper sims to analyze the effect of coral sand morphology on the starting behaviors of single-grained sediments, and to provide a reference for accurately describing the initiation of motion behavious of coral sands under hydrodynamic action of extreme waves. [Methods] We briefly analyse the difficulties in directly applying traditional equations to coral sands. Furthermore, we investigate the effect of particle size and density on initiation of motion behaviors and how nine differently shaped coral sand particles respond to extreme wave conditions through numerical calculation approaches. [Findings] The nominal diameter of these nine differently shaped coral sands is 0.589～1.696 times of their sieving diameters, followed by their corresponding wave-induced shear stress being 0.759～1.316 times, and the critical shear stress being 0.603～1.951 times of those predicted with their sieving diameters. This results in the ratio of wave-imposed shear stress to stress of sediment threshold of motion being 0.795～1.428 times of the original estimations using traditional formulae. [Conclusions] When applying quartz-based formulae to assess the possibility of coral sands being mobilized by waves, the effect of wave action may be overestimated for acicular-shaped coral sands, and underestimated for plate-shaped coral sands. Therefore, the shape of coral sand particles should be fully considered when characterizing their sediment dynamic behaviors, and therefore numerical modeling results should be adjusted accordingly with respect to particle shapes. Moreover, a more suitable description of grain size and a more accurate method measuring particle density is urgently desired for coral sand when performing hydrodynamics analysis of them.