Accurate simulation of the local scour around bridge piers in the rivers of mountainous area with uneven sandy riverbed is of great significance for the design and safe operation of the bridges. In this study, the Flow3D software was used to numerically simulate the scour around the double-row piers of Heishidu Bridge, which is built in uneven sandy riverbed. With the consideration of the suspended sediment movement process, sediment entrainment process and bed load transport process of uneven sediments in the riverbed, we marked the screened particles within each gradation range with their corresponding median particle sizes based on the particle distribution curve of the riverbed in the numerical simulation process. The obtained numerical results include detained flow field around the bridge piers, changes of riverbed scour and sedimentation, scour pits terrain morphology around the upstream and downstream piers. Under the influence of the water-blocking effect of the bridge piers, the phenomenon of water level rising in front of the piers and water level falling behind the piers can be clearly observed. Furthermore, scour pits are distributed all around the pier area, due to the protection effect of the upstream piers; the depth and scale of the pits around the downstream piers are smaller than those of the upstream piers. The numerical simulation results are in good agreement with the laboratorial test data, demonstrating the accuracy and effectiveness of the numerical calculation. The research results can contribute to the further research of local scour around bridge piers in uneven sandy riverbed.