Abstract: To study the influence of forming methods and size effects on the flexural performance of asphalt concrete, we conducted large beam bending tests on asphalt concrete in combination with the asphalt concrete wall dam project at Wusitonggou Reservoir.The test results were compared among large beam bending specimens, laboratory-formed small beam bending specimens, and field-compacted core small beam bending specimens.The results showed that: The bending strength of the on-site forming coring trabecular bending test results was 8% lower than that of indoor molding, the corresponding bending strain of bending strength was 12% higher, and the flexural modulus was 20% lower.When compared with field-paved core samples, the large-scale asphalt concrete beam demonstrated a 27% increase in bending strength, 44% growth in deformation, and a 14% reduction in flexural modulus.From the perspective of strain gradient theory, the differences among the three test results were analyzed.The yield strength of large beam bending was found to be 16% higher than that of small beam bending, which falls within the theoretical predicted range.The research findings can serve as a reference for future studies on the size effect of asphalt concrete.