To investigate the impact of load bearing strip width on the splitting tensile strength of rock-filled concrete (RFC), a discrete element model of RFC cube with a side length of 600 mm was established. In combination with the existing relevant achievements of splitting tensile strength tests on ordinary concrete and RFC cube specimens, the reasonable value of load bearing strip width in the splitting tensile strength test for large-sized RFC cube specimens was explored. The results indicate that when the load bearing strip width is less than 15 mm (relative load bearing strip width is 0.025), local shear failure occurs near the load bearing strip for the RFC cube specimens. When the relative load bearing strip width is 0.033, the influence of the load bearing strip width on the splitting tensile strength of ordinary concrete and RFC cube specimens of different sizes is relatively close. When the relative load bearing strip width is greater than 0.042, the skeletal effect of rockfill in the RFC cube specimens hinders the crack propagation, resulting in a significant increase in the influence width of the load bearing strip on the splitting tensile strength of the RFC cube specimens. It is recommended that the relative load bearing strip width for the splitting tensile strength test of large-sized RFC cube specimens be taken as 0.033.