For tunnels in frozen zone, different countermeasures should be considered for the sake of being both safe and economical when different frostheave forces are applied on the tunnel lining. Based on the case of Kunlunshan tunnel, the classification standard of the frostheave force is presented in this paper. The results show that, the frostheave force can be divided into three classes by the following two values for the singleline railway tunnels: 0.07MPa and 0.3MPa for the deep tunnels; 0.3MPa and 0.7MPa for the shallow tunnels.