Abstract: Based on random walk algorithm, a new numerical simulation method for round aggregate generation is proposed. The aggregate movement in concrete pouring and mixing is simulated. The simulation also takes gravity into account. This method can guarantee the aggregate generation successfully in one packing cycle, thus improve the efficiency of numerical simulation of concrete aggregate generation. Aggregate generation examples show the effectiveness and efficiency of the proposed numerical simulation method. They also demonstrate that this method can be used to simulate the mass, fully-graded concrete and high-strength concrete. Finally, the random walking times and packing times for the simulation were discussed.