Abstract: Based on the constuction of Fenghuoshan railway tunnel, the effect of frost forces on tunnel surpporting system in cold region is discussed. First, the elastic fomula of the frost force is given. Second,according to geological condition of rock surrounding Fenghuoshan railway tunnel, the mechanical properties of tunnel surpporting system in cold region are analyzed. And with the variation of integrity of rock,thickness and stiffness of lining, and thickness of active layer, the variation of frost force is determined. At last,based on the concept of frost damage of tunnel in cold region, some effective measures are proposed to alleviate the influence of the frost force on tunnel surpporting system in cold region. 