Many factors affect the tunnel temperature field in cold region. An unsteady heat transfer calculation model was established based on finite difference method. Taking the Nan Shan railway tunnel in cold region as an example, the othogonal test method, which takes the average temperature of tunnel lining internal nodes, lining temperature of a certain section, and longitudinal frozen length of tunnel entrance as index, respectively, is applied to carry out sensitivity study of the influencing factors on tunnel temperature field. The results show that there are some local differences in the ranging of sensitivity of each factor under different indexs. Overall, the tunnel depth, wind direction in tunnel, tunnel section size, wind speed in tunnel, wind temperature of entrance, and thermal conductivity coefficient of surrounding rock are the main factors affecting the tunnel temperature field, while the surrounding rock density and specific heat of surrounding rock are the secondary factors affecting tunnel temperature field. In the antifreezing design of the tunnel in cold region, except the unchanged factors such as the surrounding rock density, surrounding rock specific heat, surrounding rock heat transfer coefficient, thermal conductivity of surrounding rock, and wind temperature of tunnel entrance, sufficient attention should be paid on the design parameters that affect significantly the tunnel temperature field including the tunnel depth, wind direction in tunnel, wind speed in tunnel, and tunnel section size.