Based on the project of Shuangbei highway tunnel,the finite element analysis software was wsed to simulate the situation that there was the small-scale salt cavern during the construction period, and according to the critical distance calculated, a self-created device for simulating the salt cavern was taken, and then a model test with a geometric similarity ratio of 1∶25 was carried out to research the transformation law about the rock pressure,displacement of tunnel face,inner force of primary support when the tunnel was excavated to the position of critical distance and the inner pressure of the salt cavern increased until the tunnel face was broken.The results showed that,with the increases of inner pressure of the salt cavern, the tunnel face increased as almost direct proportion firstly, and then the ratio of increase became higher and higher and finally the tunnel face was broken; when the inner pressure of the salt cavern increased until the tunnel face was broken, the rock pressure showed a trend of increase in which the rock pressure of vault was the most effected location, followed by the spandrel and inflected arch, while the impact of other places was small.The bending moment distribution of steel arch is almost the same as the inner force of salt cavern increased.And as the inner force of salt cavern increased, the bending moment of vault and inverted arch showed a trend of increase in which the most effected location was focused on the vault and inverted arch while other location was less effected; what’s more, with the increases of the inner force of salt cavern, the axial force of steel arch all showed a trend of increase, and the most effected location was the vault, followed by the right and left haunch while the impact of inverted arch and spandrel were little; effected by the inner force of salt cavern change, the rock pressure,displacement of tunnel face,inner force of primary support all showed the ratio of change became faster and faster.