Abstract: Aseismatic calculation was used for the analysis on open tunnels of freeway for an important practical engineering project.The response of acceleration and internal forces of structure were described,and then the safety of structures embedded at different depths of soil was discussed.It was shown that key points controlling the structure design were the locations of the basement of sidewall and the middle part of inverted arch.The safety factor of supporting structure would decrease with the increase of thickness of filled soil,and the shoulder of arch would become the critical position of stability.