Abstract: The critical state is a very important concept in soil mechanics, and it is the foundation of many constitutive models for soils. As for the coral sand, due to significant particle breakage, its deformation characteristics and critical state are worthy of further study. To study the effect of particle breakage on the deformation characteristics and critical state of soils, a series of triaxial tests with different densities and confining pressures are carried out. A mathematical expression for the critical state of the coral sand considering particle breakage is proposed, and introduced into the state-dependent dilatancy equation for the coral sand. The state-dependent dilatancy equation and constitutive model of the coral sand considering particle breakage are proposed. The stress and deformation characteristics of the coral sand with different densities and confining pressures can be well reflected by using only one set of model parameters, and the particle breakage characteristics of the coral sand can be considered.