In this study, a diaphragm walled excavation in Macao alluvium was investigated using finite element method. Macao alluvium is composed mainly of sand with varying fine content and exhibits a wide range of engineering properties, which presents a major problem for determination of design parameters and selection of modeling methodology. In selection of soil parameters, Equivalent Young's modulus approach based on previous experience of similar excavations was adopted. Both linear and nonlinear elasto-plastic soil constitutive models were selected to simulate the properties of alluvial soil. Namely, Mohr-Coulomb model (MC) and Lade model (LD). The calculated wall deflection and settlement compared favorably with observations when appropriated mean soil stiffness is assessed. The soil model which is capable in modeling soil deformation would provide better prediction of ground settlement.