Based on observed temperature values in Beiluhe on Qinghai–Tibet Plateau, this paper sets up a regression equation using statistics methods between the temperature at shallow ground depth (0.5 m)and the direct solar radiation on embankment horizontal surface. There is a good linear relation between the temperature and the solar radiation after the phase difference is removed. Correlation coefficient R2 is 0. 9321, and the regression equation is: T = aQ – b where, T—temperature (°C) on horizontal surface of shallow ground (0.5m); Q—solar radiation after the phase difference is removed (W.m-2); a,b—constants, is 0.5552and 16.549, respectively. The equation is validated and allows the temperature on horizontal surface of railway embankments. Whether it applies to other places needs further study. And based on this conclusion, combining with the law of documents and materials, and considering local factors, such as vegetative cover, snow, lithology, soil moisture and so on, we further prove there is obvious linear relation between the temperature and the direct solar radiation on horizontal surface.