Abstract: Vehicle bump at the bridge-head is a common disease fromdifferential settlement between bridge structure and approach fill in a superhighway.In engineering, there is no ideal remedy for it, because the commonbridge abutment fill cannot be compacted effectively. In recent years, a new type abutment -- flexible abutment was applied in engineering,which may prevent differential settlement radically. But its reinforced interval valuewas determined blindly. In this article,4 groups of model tests were carried out for comparative analysis. The tests indicated that the bestreinforced interval value was between 30cm and 50cm.