The natural environment in which bridges are located varies widely. In order to ensure the normal use of the pylon structure, it is necessary to study the influence of different external environmental factors on the temperature field and temperature effect of the pylon. The purpose of this paper is to study the temperature effect of a cable-stayed bridge in the PC part of the railway based on long-term monitoring. The relevant theories of temperature field and temperature stress analysis are summarized, and the main girder section temperature monitoring scheme is designed according to the interpolation fitting criteria. As the comparative weak radiation day temperature data, the temperature variation law of the box girder section is analyzed, and the temperature gradient fitting curve is obtained by the regression fitting method. The temperature boundary is established according to astrophysics and heat transfer theory, and the temperature field distribution and temperature stress state of the main beam are analyzed by ANSYS two-dimensional box girder section model and Midas/Civil full bridge model. The experimental results show that the solar short-wave radiation is a The main factor that causes the temperature difference of box girder section.