The trenching construction of a single diaphragm wall is simulated using the three-dimensional finite element method. The influences on the soil lateral movements and surface settlements of the factors, including the slurry pressure, the depth, width, and thickness of the wall are studied. It has been found that the soil lateral movements and surface settlements are sensitive to the slurry pressure and the width of the diaphragm wall, while the influence of the thickness of the wall is smaller. The results also show that when the depth of the wall is biger than a certain value, and the variation of the depth of the wall has little effect on the maximum soil lateral movement and surface settlement.