To study the impact of spatial randomness of the gradation parameter on the deformation and stress of rockfill dams, the fractal model was selected to describe the gradation distribution. The exponential model and the Gauss model were introduced as the variogram model to analyze the spatial varying structure of gradation fractal dimension D, and some geological statistical methods such as the Kriging method were introduced to simulate the spatial random distribution of gradation parameters of rockfill material and transition material in the Lianghekou core-wall rockfill dam. With the combination of stochastic modeling and finite element method, this paper carried out 500 deformation and stress simulations for the dam to obtain the convergent results and compared the results with the deterministic finite element method. It is determined that when the spatial variability of rockfill materials is considered, the maximum displacement in horizontal direction and the maximum settlement will increase. Therefore, when the spatial variability is not considered, the probability of underestimating dam stress and deformation will exceed 50%. The calculation method considering the spatial random distribution of gradation parameter has good application value for the design and deformation control of high rockfill dams.