Abstract: Water kiln is a kind of catchments and conservancy project to retain rainfall so as to meet the needs of human beings, animals and saved irrigation. It belongs to a special underground structure with small depth of burial and without liner based on its mechanical characteristics. The stability and safety of kiln is determined by its structure shape and shape parameters. The excavation stage is one of hazardous stages due to construction perturbation and unloading of surrounding kiln soil body. The excavation process was divided into upward and downward excavation methods. Using nonlinear clasto-plastic analysis method, the excavation process of practical water kiln designed was simulated according to the shape and parameters of inclined-wall round-arched kiln determined by primary research. Effects of excavation loads on the stability of kiln were analyzed from three aspects of displacements, plastic zones and soil tensile stresses. The numerical simulation results show that the soil body of water kiln is stable in spite of upward or downward excavation method. The rationality of water kiln shape parameters and arch curve equation proposed by primary research are validated and its calculation theory and method can be applied to the design of water kiln.