The impact of frost heave on open cut tunnels is often neglected for seasonally frozen tunnels at low altitudes. However, these tunnels are highly susceptible to frost damages. Therefore, in order to ensuring normal operation and driving safety, the researches on effective thermal insulation measures for open cut tunnels in seasonally frozen regions is significantly important. Based on the Hangou No. 2 Tunnel which is in the low-altitude seasonally frozen region, a heat-stress numerical model was established by Comsol Multiphysics finite element software and the temperature changes of surrounding rock for various locations of insulation layer was analyzed. The temperature distributions of the open cut tunnel and stress distributions of tunnel lining were studied for different insulation layer thicknesses and backfill thicknesses. The results show that the insulation effects are very good when the insulation layer is placed outside or inside of the open cut tunnel lining. When there is no insulation layer the surrounding rock temperature. at the crown is negative It is easy to result in bi-directional freezing and the maximum peak stress of the crown lining is up to 938 kPa. When 6 cm insulation layer is used the maximum peak stress of the crown lining is reduced to 547 kPa, which is decreased by 71%. The greater the insulation layer thickness and backfill thickness, the more favorable the surrounding rock temperature distribution, and the smaller the tunnel lining stress. The research results can provide references and recommendations for establishing insulation plan of similar open cut tunnels in seasonally frozen regions.