Abstract: Rock-soil filled roadbed has been broadly adopted in western mountain areas in China.Because the design and construction criteria were not perfect,asymmetrieal settlement often occurred,then settlement or deformation was caused,and the service level of the road was descended.To post the settlement mechanism of the rock-soil filled roadbed,and to provide basis for design and construction,2D mechanical model tests were carried out on rock-soil filled roadbed with different densities and operating modes.The tests reappeared the process and the final mode of the settlement.It was shown that the height and density of the rock-soil filled roadbed were the major factor of influence on the settlement.The settlement during construction was much bigger than that after the construction,and the settlement during the construction increased parabolaically with the roadbed height and developed very quickly,while the settlement after the construction increased linearly and developed rather slowly.The final settlement of low density roadbed might be twice of that of high density roadbed.