Based on 3D modeling and PFC 5.0 platform FISH language，a method for constructing aggregate 3D discrete element model was developed. The aggregate particle geometry was constructed based on three-dimensional modeling and the aggregate geometry was imported into the PFC 5.0 platform to construct a clump template that can characterize the aggregate geometry. Then，clump template was called to generate clump in a certain space for aggregate discrete element simulation. In order to evaluate the effectiveness and accuracy of the method，the degree of filling was used to evaluate the effect of clump on the geometry of the aggregate and the number of unit spheres was used to quantify the impact of virtual aggregates on computational efficiency. The relationship between geometric shape accuracy and the efficiency of the filling algorithm was analyzed. In addition，the effect of fill algorithm parameters on fill level and number of unit spheres was explored. The results show that the number of geometrical feature points of aggregates is 1 000 ~ 2 000，which can take advantage of the filling algorithm. The clump block generated by the recommended parameters of the filling algorithm can better balance the filling precision and calculation efficiency. The method can realize the low-cost and high-efficiency generating three-dimensional discrete element model of aggregate，and provide powerful technical support for further digital test piece simulation.