Abstract: Rock-filled concrete (RFC) is an emerging casting technology for large-scale concrete construction and it has been used in many projects in hydraulic engineering. In this work, we have developed a two-dimensional particle-based discrete element model of RFC and investigated three influence factors on RFC strength, i.e. arrangement pattern of rock aggregates, strength of self-compacting concrete (SCC), and strength of interface between SCC and rocks. The numerical results show that the packing pattern of rock aggregates significantly affects RFC strength. Higher compressive strength is shown in cases where the applied load is carried by rock aggregates than those cases where the load is supported by both constituents. RFC strength becomes higher with increasing strength of interfaces or SCC. However, the compressive strength of RFC may approach its maximum value when the strength of SCC increases up to a certain value, and it is subsequently determined by the arrangement pattern of rock aggregates and the strength of interfaces.