A 3D stochastic modeling was carried out to simulate the dendritic grains during solidification of aluminum alloys,including time-dependent calculations for temperature field, solute redistribution in liquid, curvature of the dendritictip, and growth anisotropy. The nucleation process was treated by continuous nucleation. A 3D simplified grainshape model was established to represent the equiaxed dendritic grain. Based on the Cellular Automaton method,a grain growth model was proposed to capture the neighbor cells of the nucleated cell. During growing, each graincontinues to capture the nearest neighbor cells to form the final shape. When a neighbor cell was captured by othergrains, the grain growth along this direction would be stopped. Three-dimensional calculations were performed tosimulate the evolution of dendritic grain. In order to verify the modeling results, the predictions were compared withthe observation on samples cast in the sand mold and the metal mold.