The construction process of a foundation pit of Honggu Tunnel adjacent to river in Nanchang under heaped load is simulated by finite element software ABAQUS so as to study the characteristics of the retaining structures of the foundation pit. The simulation results show that the heaped load affects the underground diaphragm wall a lot. The point of maximum horizontal displacement of underground diaphragm wall along vertical direction rises with heaped load increase. It is suggested that the heaped load should be less than 60 kPa.