In order to study the splitting tensile properties of early-age concrete, a 3D meso-concrete model with a 35% coarse aggregate volume content was established using Python scripting language for secondary development based on ABAQUS software platform. 3D zero-thickness cohesive elements were embedded in the mortar elements interface and the mortar-aggregate interface transition zone (ITZ). The splitting tensile strength of concrete cylinders with three mesh sizes of 4,5 and 6 mm and different ages were simulated. The results show that the combination of 3D random polyhedral aggregates meso-concrete model and cohesive elements is suitable for the fracture simulation of early-age concrete cylinders, which can not only accurately show the geometric shape and spatial distribution of actual aggregates, but also predict the mechanical properties and failure state of concrete with a high degree of visualization. The three different mesh sizes have minimal influence on the splitting tensile strength, but they do have some influence on the descending section of load-displacement curves. The maximum error between the calculated value of the formula, the simulated average value and the test value is 17.65% and 16.18% at the first day, and the errors are less than 5% in other ages, which validates the applicability and reliability of the model. The failure processes and final failure states of models at different ages are similar. Microcracks initiate and propagate in the ITZ, and localized areas of concrete experience crushing, ultimately resulting in vertical main cracks that traverse the cross-section of the concrete cylinder.